I don't know much about the plants and wildlife out here, but I'm learning.
The table was decorated with rare and beautiful plants and flowers.
This is due in part to the different physical conditions there prevailing and in part to the invasion of the north-eastern portion of the continent by a number of plants characteristically Melanesian.
The book provided excellent examples of the plants and she found a large assortment of edible foods.
The plants died, the lakes dried up.
Tables and shelves were stacked with dozens of potted plants of various sizes, each in separate boxes.
I've identified twenty-five plants on this trek.
"Do humans eat plants?" she asked, eyes on the illustration.
Natural gas, piped from the Kansas fields, is used for light and power, and electricity for commercial lighting and power is derived from plants on Spring River, near Vark, Kansas, and on Shoal creek.
Colsa, grown chiefly in the lower basin of the Seine (SeineInfrieure and Eure), is the most important of the oil-producing plants, all of which show a diminishing acreage.
The walls were filled with books while plants added to the warm and homey atmosphere.
The plants she had started in the house in March thrived.
I took Helen and my Botany, "How Plants Grow," up in the tree, where we often go to read and study, and I told her in simple words the story of plantlife.
We don garment after garment, as if we grew like exogenous plants by addition without.
What about the plants you're growing?
Plants are as well.
Humans require relatively little oxygen, and plants are constantly transforming the carbon dioxide we exhale back into useful oxygen.
They are herbaceous plants growing from an underground much ?
Do you know how many edible plants grow naturally in our own front yards?
Thus we had genetic modifications in plants that could have occurred in nature but probably wouldn't have.
We gladly allowed her to use freely our library of embossed books, our collection of stuffed animals, sea-shells, models of flowers and plants, and the rest of our apparatus for instructing the blind through the sense of touch.
They shelter in crevices of the bark of trees, in the dried stems of herbaceous plants, or among moss and fallen leaves on the ground.
The comparative richness of proteaceous plants in Western Australia and South Africa first suggested a common source for these primitive types.
Their nets, made by women, either of the tendons of animals or the fibres of plants, will catch and hold the kangaroo or the emu, or the very large fish of Australian rivers.
At Bajo de Velis, in San Luis, the plants belong to the " Glossopteris flora," which is so widely spread in South Africa, India and Australia, and the beds are correlated with the Karharbari series of India (Permian or Permo-Carboniferous).
Out there in the woods lay a multitude of plants she wanted to see, and no slithering reptile was going to stand in her way.
Forbes drew attention to a certain community amongst birds and other vertebrates, invertebrates, and amongst plants, on all the lands stretching towards the south pole.
Elsewhere the plants generally indicate a higher horizon and are considered to correspond with the Rhaetic of Europe_ Jurassic beds are known only in the Cordillera itself, and the Cretaceous beds, which occur in the west of the country, are of freshwater origin.
Proteaceous plants, although not exclusively Australian, are exceedingly characteristic of Australian scenery, and are counted amongst the oldest flowering plants of the world.
We don't know if the cause is the power sources, some or more of the plants or the room itself.
animals, plants and minerals (ThierKrc caterand Bergbuch).
Cepa, dating from about the beginning of the Christian era (Origin of Cultivated Plants, p. 71).
I feel like a criminal driving over these beautiful plants and flowers.
"Humans eat plants and macaronis and –" "Meatballs!"
So far this form of winning is chiefly carried on in New South Wales, where there are about fifty gold-dredging plants in successful operation.
Sensors can constantly monitor moisture levels in the soil, the size and color of the plants, air quality, nutrient levels in the soil, amount of sunlight, and hundreds of other variables.
The basement area was considerably larger than Quinn's small cabin lab-room, noticeably so with fewer plants and absent the desk.
We don't even know if the plants have anything to do with it.
She pulled the rocker to the edge of the porch and lifted the plants to some hooks.
The anatomical construction of these plants presents many peculiarities which have given rise to discussion as to the allocation of the order among the dicotyledons or among the monocotyledons, the general balance of opinion being in favour of the former view.
Many instances are on record of symptoms of poisoning, and even death, having followed the consumption of plants which have passed as true mushrooms; these cases have probably arisen from the examples consumed being in a state of decay, or from some mistake as to the species eaten.
How good a job are the plants doing?
Where transgenesis offers the most amazing possibilities is in GM foods because it allows plants to exceed their maximum genetic potential.
She wanted to know who made fire under the ground, and if it was like the fire in stoves, and if it burned the roots of plants and trees.
I had often since seen its crumpled red velvety blossom supported by the stems of other plants without knowing it to be the same.
Well, then, come here, said she, and went further in among the plants and threw down the doll.
The lake is nowhere of great depth, and about midway numerous mud-banks, marshes, islands and dense growths of aqueous plants stretch across its surface.
Dorothy and Zeb now got out of the buggy and walked beside the Prince, so that they might see and examine the flowers and plants better.
My daughter, the family gardener, only plants heirloom produce from non-hybrid seeds.
I had no difficulty in making it clear to her that if plants and animals didn't produce offspring after their kind, they would cease to exist, and everything in the world would soon die.
The plants were grown from the remains of my forefathers?
The plants are grown in the stove till the flowering period, when they may be removed to the greenhouse.
Evergreens predominate in the south, where grow subtropical plants such as the myrtle, arbutus, laurel, holm-oak, olive and fig; varieties of the same kind are also found on the Atlantic coast (as far north as the Cotentin), where the humidity and mildness of the climate favor their growth.
Inside the hedge they came upon row after row of large and handsome plants with broad leaves gracefully curving until their points nearly reached the ground.
No truths brought to light by biological investigation were better calculated to inspire distrust of the dogmas intruded upon science in the name of theology than those which relate to the distribution of animals and plants on the surface of the earth.
Gray desert plants, notably cactuses and other thorny plants, partly replace in the south the bushes of the north.
Plants themselves are pretty inefficient machines, at least from the standpoint of being good food sources for us.
To deal in generalities, plants capture, on average, about 5 percent of the solar energy that falls on their leaves.
Then he noticed when he bred tall pea plants with another tall plant, he occasionally got a short offspring, but usually tall ones.
Plus, raising plants and animals takes a long time and is a lot of work to boot.
Wouldn't that be something: Plants that would convert nitrogen from the atmosphere directly into ammonia they could use or plants that gave off the odor of other plants that pests avoid?
Sunscreens for plants protects them from ultraviolet and infrared radiation.
Different techniques could be applied to different plants side by side to constantly be refining agricultural processes.
Atmospheres will form, then plants will be seeded, and then the colonists will arrive.
Those plants of whose greenness withered we make herb tea for the sick serve but a humble use, and are most employed by quacks.
In almost all climes the tortoise and the frog are among the precursors and heralds of this season, and birds fly with song and glancing plumage, and plants spring and bloom, and winds blow, to correct this slight oscillation of the poles and preserve the equilibrium of nature.
Quinn is packing up the power sources as we speak and the plants will be destroyed as part of the test.
"The location is the big difference and there are fewer plants," I said.
That proves it isn't the plants or location that are the cause of your visions.
She inched away from a plant whose slender stalk was maneuvering through several other plants to position its leaves in direct sunlight.
Rhyn clenched his fists. Darkyn said nothing else and walked away, disappearing into the morning shadows of the forest. Rhyn felt fevered. His power was leaking out of his body, killing the plants around him. He grappled to control what he could, aware he would soon not have that option.
The tomato plants were drooping, their crop reduced to small discolored fruit.
I have some hanging plants I've been trying to get rid of that would look great on your front porch.
It is the principal genus of the natural order of Monocotyledous Potamogetonaceae, and contains plants with slender branched stems, and submerged and translucent, or floating and opaque,.
Large tracts of mountain are clothed with fragrant scrub composed of these and other plants.'
A collection of woody plants, one of the largest and finest in the world, and a broad forest and hunting preserve, known as Pisgah Forest (ioo,000 acres), are also maintained by the owner.
For Flora: Maiden, Useful Native Plants of Australia (Sydney, 1889); Bentham and Mueller, Flora Australiensis (London, 1863-1878); Fitzgerald, Australian Orchids (Sydney, 1870-1890); Mueller, Census of Australian Plants (Melbourne, 1889).
They have sequenced the cacao tree, the mosquito, coral, the Tasmanian devil, the bald eagle, the leafcutter ant, a germ that attacks wheat plants, and the extinct woolly mammoth.
A fascinating character and an extremely patient experimenter, Mendel was a German friar and scientist who figured out that plants (and presumably animals) had inheritable characteristics.
I've set up the same old power sources as New Hampshire and I managed to gather up about a third of the same plants.
Make a note of the exact settings after you remove all your plants.
I am not pleased by these mortal plants.
According to the pictures, there would be plants.
Did you eat one of the plants?
Megan stood and smiled a genuine welcome as Clara emerged from the car, carrying two large hanging plants.
In the kitchen they sipped tea and discussed everything from wildlife to house plants.
Muldrow had said the land was overgrown with edible plants.
Thysanoptera are found on the leaves and in the blossoms of plants.
mushroom has numerous varieties, and it differs in different places and under different modes of culture in much the same way as our kitchen-garden plants differ from the type they have been derived from, and from each other.
It is grown in conservatories for half-hardy plants.
These older beds are overlaid, especially in the western part of the country, by a sandstone series which contains thin seams of coal and many remains of plants.
Among the plants the wild banana, pepper, orange and mangosteen, rhododendron, epiphytic orchids and the palm; among mammals the bats and rats; among birds the cassowary and rifle birds; and among reptiles the crocodile and tree snakes, characterize this element.
the soil to the depth of many feet, and from it springs the most marvellous tangle of huge trees, shrubs, bushes, underwood, creepers, climbing plants and trailing vines, the whole hung with ferns, mosses, and parasitic growths, and bound together by rattans and huge rope-like trailers.
Among indigenous fruitbearing trees, shrubs, vines and plants are the plum, cherry, grape, blackberry, raspberry, cranberry and strawberry.
A few of the medicinal plants are ginseng, pleurisy root, snake root, blood root, blue flag and marshmallow.
Orchids are very prominent among a great variety of flowering plants.
Along the shore of Lake Champlain are a few species of maritime plants that remain from the time when portions of western Vermont were covered by the sea, and on the upper slopes of some of the higher mountains are a few Alpine species; these, however, are much less numerous on the Green Mountains of Vermont than on the White Mountains of New Hampshire.
GUACO, Huaco or Guao, also Vejuco and Bejuco, terms applied to various Central and South American and West Indian plants, in repute for curative virtues.
The soil is in general very fertile, the principal products being rice, maize and pulse (kachang) in the lower grounds, and cinchona, coffee and tea, as well as cocoa, tobacco and fibrous plants in the hills.
Its flat-roofed Moorish houses are enclosed by gardens of cactus, dwarf palm, orange and other subtropical plants, interspersed with masses of rock.
serere, to sow), the fertilized ovule of plants.
The seeds of the cryptogams or flowerless plants are not true seeds and are properly designated "spores."
PITCHER PLANTS, in botany, the name given to plants in which the leaves bear pitcher-like structures or are pitcher-like in form.
They are shrubby plants climbing over surrounding vegetation by means of tendrillike prolongations of the midrib of the leaf beyond the leaf-tip.
Thus Nepenthes secures a supply of nitrogenous food from the animal world in a manner somewhat similar to that adopted by the British sundew, butterwort, and other insectivorous plants.
Throughout the region north of the Apennines no plants will thrive which cannot stand occasional severe frosts in winter, so that not only oranges and lemons but even the olive tree cannot be grown, except in specially favoured situations.
and textile plants.
Among the chief industrial plants is tobacco, which grows wherever suitable soil exists.
The yield for 1901 was 5528 tons, but a large increase took place subsequently, eleven million new plants having been added in southern Italy in 1905.
Tile chief textile plants are hemp, flax and cotton.
The supposition that sensation thus rests on a material process of absorption from external bodies naturally led up to the idea that plants and even inorganic subtances are precipient, and so to an indistinct recognition of organic life as a scale of intelligence.
or vital principle, with heat or fire which pervades in unequal proportions, not only man and animals, but plants and nature as a whole, and through the agitation of which by incoming effluvia all sensation arises.
Individual things are supposed to arise out of the original being, as animals and plants out of seeds.
The superiority of animals to plants and metals in the possession of special organs of sense is connected with the greater complexity and heterogeneity of their structure.
There are three stadia, or moments, in this process of nature - (i) the mechanical moment, or matter devoid of individuality; (2) the physical moment, or matter which has particularized itself in bodies - the solar system; and (3) the organic moment, or organic beings, beginning with the geological organism - or the mineral kingdom, plants and animals.
The notion that all the kinds of animals and plants may have come into existence by the growth and modification of primordial germs is as old as speculative thought; but the modern scientific form of the doctrine can be traced historically to the influence of several converging lines of philosophical speculation and of physical observation, none of which go further back than the 17th century.
The observation of the existence of an analogy between the series of gradations presented by the species which compose any great group of animals or plants, and the series of embryonic conditions of the highest members of that group.
In the then state of knowledge, it appeared that all the species of animals and plants could be arranged in one series, in such a manner that, by insensible gradations, the mineral passed into the plant, the plant into the polype, the polype into the worm, and so, through gradually higher forms of life, to man, at the summit of the animated world.
Taking into account existing animals and plants alone, it became obvious that they fell into groups which were more or less sharply separated from one another; and, moreover, that even See the " Historical Sketch " prefixed to the last edition of the Origin of Species.
The conclusions enunciated by Cuvier and Von Baer have been confirmed in principle by all subsequent research into the structure of animals and plants.
The apparently clear distinction between flowering and flowerless plants has been broken down by the series of gradations between the two exhibited by the Lycopodiaceae, Rhizocarpeae, and Gymnospermeae.
Such a condition has been termed, with regard to the group of animals or plants the organs of which are being studied, archecentric. The possession of the character in the archecentric condition in (say) two of the members of the group does not indicate that these two members are more nearly related to one another than they are to other members of the group; the archecentric condition is part of the common heritage of all the members of the group, and may be retained by any.
Nevertheless, under some of these flows remains of plants and insects of species now living in the islands have been found - a proof that the formation as well as the denudation of the country is, geologically speaking, recent.
The same belief is shown in the botanical names applied to many plants, e.g.
The astrological belief that plants, animals and minerals are under the influence of the planets is shown in the older names of some of the metals, e.g.
Saturn for lead, Venus for copper, and Mars for iron, and the belief that the colours of flowers ' The Egyptians believed that the medicinal virtues of plants were due to the spirits who dwelt within them.
In the most generally used sense, a plant is a member of the lower or vegetable order of living organized things; the term is also popularly applied to the smaller herbaceous plants, thus excluding trees and shrubs.
Some account of the history of plant classification and the development of a natural system in which an attempt is made to show the actual relationships of plants, is given in the article BOTANY.
The plant world falls into two great divisions, the higher or flowering plants (Phanerogams), characterized by the formation of a seed, and the lower or flowerless plants (Cryptogams), in which no seed is formed but the plants are disseminated by means of unicellular bodies termed spores.
in many Cryptogams than in the flowering plants.
Thallophyta are the most lowly organized plants and include a great variety of forms, the vegetative portion of which consists of a single cell or a number of cells forming a more or less branched thallus.
They are characterized by the absence of that differentiation of the body into root, stem and leaf which is so marked a feature in the higher plants, and by the simplicity of their internal structure.
In general structure they approach the Phanerogams with which they form collectively the Vascular Plants as contrasted with the Cellular PlantsThallophyta and Bryophyta.
The sporophyte is the plant which is differentiated into stem, leaf and root, which show a wonderful variety 01 form; the internal structure also shows increased complexity and variety as compared with the other group of vascular plants, the Pteridophyta.
The Spermatophyta are thus land plants par excellence and have, with the few exceptions cited, lost all trace of an aquatic ancestry.
Aquatic plants occur among seed plants but these are readaptations of land plants to an aquatic environment.
ANATOMY OF PLANTS
An account of the structure of plants naturally begins with the cell which is the proximate unit of organic structure.
1.Examples of the differentiation of the cells of plants.
For a more detailed description of the cell see CYTOLOGY and the section on Cytology of Plants below).
In the higher (more complicated) plants the cells differ very much among themselves, and the body is composed of definite systems of these units, each system with its own characteristic structure, depending partly on the characters of the component cells and partly)~ I ill N~V O~V~
ia.Examples of the differentiation of the tissue of plants.
It is convenient here to define the two chief types of cell-form which characterize tissues of the higher plants.
This differentiation is parallel with that between stem and leaf of the higher plants.
Cells of this type are often called trumpet-hyphae (though they have no connection with the hyphae of Fungi), and in some genera of Laminariaceae those at the periphery of the medulla simulate the sieve-tubes of the higher plants in a striking degree, even (like these latter) developing the peculiar substance callose on or in the perforated cross-walls or sieve-plates.
A specialized conducting tissue of this kind, used mainly for transmitting organic substances, is always developed in plants where the region of assimilative activity is local in the plant-body, as it is in practically all the higher plants.
The formation of a massive body naturally involves the localization of the absorptive region, and the function of absorption (which in the simpler forms is carried out by the whole of the vegetative part of the mycelium penetrating a solid or immersed in a liquid substratum) is subserved by the outgrowth of the hyphae of the surface-layer of that region into rhizoids, which, like those of the Algae living on soil, resemble the root-hairs of the higher plants.
But these two principles do not find their full expression till we come, in the ascending series, to the Vascular Plants.
morphological identity) between the differentiated tissues of an Anthocerotean sporogonium and those of the sporophyte in the higher plants.
Thus the histological differentiation of the sporogonium of the higher mosses is one of considerable complexity; but there is here even less reason to suppose that these tissues have any homology (phylogenetic community of origin) with the similar ones met with in the higher plants.
In higher forms the conducting strands of the leaves are continued downwards into the stem, and eventually come into connection with the central hydrom cylinder, forming a complete cylindrical investment apparently distinct from the latter, and exhibiting a differentiation into hydrom, leptom and amylom which almost completely parallels that found among the true vascular plants.
ferns, horse-tails, club mosses, &c., and Phanerogams or Flowering Plants) the main plant-body, that which we speak of in ordinary language as the plant, is called the sporophyte because it bears the asexual reproductive cells or spores.
The body of the sporophyte in the great majority of the vascular plants shows a considerable increase in complexity over that found in the gametophyte of Bryophytes.
trace a three-fold division of tissue systems, a division of which there are indications among the lower plants, and which is the expression of the fundamental conditions of the evolution of a bulky differ- Tissue entiated plant-body.
In the typically submerged Alg~ and in submerged plants of every group this is the absorptive and the main.
Terrestrial plants have a gaseous interchange of oxygen and carbon dioxide which is necessary for respiration and feeding.
In the Vascular Plants this tissue is collectively known as the vascular system.
The structure of the stomata of the sporophyte of vascular plants is fundamentally the same as that of the stomata on the sporogonium of the true mosses and of the liverwort A nihoceros.
This type of structure, which is extremely various in its details, is found especially, as we should expect, in plants which have to economize their water supply.
This is found especially in plants which during certain hours of the day are unable to cover the water lost through transpiration by the supply coming from the roots.
In a second type they are situated at the ends of tracheal strands and consist of groups of richly protoplasmic cells belonging to the epidermis (as in the leaves of many ferns), or to the subjacent tissue (the commonest type in flowering plants); in this last case the cells in question are known as epithem.
types of glands also exist, either in connection with the epidermis or not, such as nectaries, digestive glands, oil, resin and mucilage glands, &c. They serve the most various purposes in the life of the plant, but they are not of significance in relation to the primary vital activities, and cannot be dealt with in the limits of the present article.l The typical epidermis of the shoot of a land plant does not absorb water, but some plants living in situations where they cannot depend on a regular supply from the roots (e.g.
epiphytic plants and desert plants) have absorptive hairs or scales on the leaf epidermis through which rain and dew can be absorbed.
bodies of the higher plants its functions are numerous.
In all green plants which have a special protective epidermis, the cortex of the shoot has to perform the primitive fundamental function of carbon assimilation.
The leaves of shade plants have little or no differentiation of palisade tissue.
One of the most striking characters common to the two highest groups of plants, the Pteridophytes and Phanerogams, is the Vascular possession of a double (hydrom-leptom) conducting .s system, such as we saw among the highest mosses, YS em.
The stelar system of Vascular Plants has no direct phylogenetic connection with that of the mosses.
Vessels are common in the Angiospermous group of Flowering Plants.
ft1.Types of Stole in Vascular Plants.
We now know that many at least of the Cycadofilices bore seeds, of a type much more complex than that of most modern seed plants, and in some cases approximating to the seeds of existing Cycads.
confined to the stem) such as are found in the dictyosteles of ferns are rare in the flowering plants.
The constitution of the stele of a flowering plant entirely from endarch collateral bundles, which are either themselves leaf-traces or will form leaf-traces after junction with other similar bundles, is the great characteristic of the stem-stele of flowering plants.
similar phenomenon is seen in two r widely separated genera of flowering plants: Primula Auricula and Gunnera (Halorageae).
The radial structure is characteristic of all root-steles, which have in essential points a remarkably uniform structure throughout the vascular plants, a fact no doubt largely dependent on the very uniform conditions under which they live.
The use of certain plants as rubber-producers (notably Hevea b~-a~iliensis, the Pam rubber-tree) depends on this property.
Later, the axis branches by the formation of new growing-points, and in this way the complex system of axes forming the body of the ordinary vascular plant is built up. In the flowering plants the embryo, after developing up to a certain point, stopf growing and rests, enclosed within the seed.
The triple division of tissues is laid down in most cases at 1 very early period of developmentin the flowering plants usuall3 before the resting stage is reached.
In the seed-forming plants (Phanerogams) one or more primary leaves (cotyledons) are already formed in the resting embryo.
In most of the existing Pteridophytes, in the Monocotyledons and in annual plants among the Dicotyledons, there is n further growth of much structural importance in the ~ d ~
The formation of secondary tissues is characteristic of most woody plants, to whatever class they belong.
Every great group or phylum of vascular plants, when it has become dominant in the vegetation of the world, has produced members with the tree habit arising by the formation of a thick woody trunk, in most cases by the activity of a cambium.
The vessels and tracheids are very various in size, shape and structure in different plants.
The limit of each years increment of secondary wood, in those plants whose yearly activity is interrupted by a regular winter or dry season, is marked by a more or less distinct line, which is produced by the sharp contrast between the wood formed in the late summer of one year (characterized by the sparseness or small diameter of the tracheal elements, or by the preponderance of fibres, or by a combination of these characters, giving a denseness to the wood) and the loose spring wood of the next year, with its absence of fibres, or its numerous large tracheae.
In many annual plants no cambium is formed at all, and the same is true of most perennial Pteridophytes and Monocotyledons.
When the vascular tissue of such plants is arranged Camblum in separate bundles these are said to be closed.
The in Stems. bundles of plants which form cambium are, on the contrary, called open.
Irregularity of cambium occurs in various families of woody dicotyledonous plants, mostly among the woody climbers, known as lianes, characteristic of tropical and sub-tropical forests.
The cambium in the root, which is found generally in those plants which possess a cambium in the stem, always begins in the conjunctive tissue internal to the primary phloems, and Camblum forms new (secondary) phloem in contact with the In Roots primary, and secondary xylem internally.
In nearly all plants which produce secondary vascular tissues by means of a cambium there is another layer of secondary meristem arising externally to, but in quite the same fashion as, Ph II
A peculiar modification of periderm is formed by the phellogen in the submerged organs (roots or stems) of many aquatic or marsh-loving plants.
Secondly, the histology of fossil plants, particularly woody plants of the carboniferous period, has been placed on a sound basis, assimilated with general histological doctrine, and has considerably enlarged our conceptions of plant anatomy as a whole, though again.
of Fossil Plants of the Coal Measures (Phil.
recent years, of Zeiller in France, and Scott, Seward and others in England, has advanced our knowledge of the anatomy of ~fossil plants in an important degree.
the recognition within the last few years of the existence of an extinct group of plants lying on the borderland between.
A very considerable body of knowledge relating to this subject already exists, but further work on experimental lines is urgently required to enable us to understand the actual economy of plants growing under different conditions of life and the true relation of the hereditary anatomical characters which form the subject matter of systematic anatomy to those which vary according to the conditions in which the individual plant is placed.
PHYSIOLOGY OF PLANTS
This is evident in the case~ of such plants as have a body consisting of filaments or plates of cells, and is little less conspicuous in those whose mass is but small, though the cells are evidently capable of computation in three dimensions.
It does not at first appear to be the same with the bulkier plants, such as the ordinary green herbs, shrubs or trees, but a study of their earlier development indicates that they do not at the outset differ in any way from the simple undifferentiated forms. Each commences its existence as a simple naked protoplast, in the embroyo-sac or the archegonium, as the case may be.
In this matter, differentiation has proceeded very differently in animals and plants respectively, no nerves or sense organs being structurally recognizable.
There can be no doubt that there is no fundamental difference between the living substance of animals and plants, for many forms exist which cannot be referred with certainty to either kingdom.
The latter function has been found to be of extreme importance in the case of plants exposed to the direct access of the suns rays, the heat of which would rapidly cause the death of the protoplasts were it not employed in the evaporation of the water.
The natural source of the water is in all cases the soil, and few plants normally obtain any from elsewhere.
Nature of the Food of Planls.The recognition of the fundamental identity of the living substance in animals and plants has directed attention to the manner in which plants are nourished, and especially to the exact nature of their food.
The idea was till recently currently accepted, that anything which plants absorbed from without, and which went to build up their organic substance, or to supply them with energy, or to exert some beneficial influence upon their metabolism, coiistituted their food.
Now, as the materials which plants absorb are carbon dioxide from the air, and various inorganic compounds from the soil, together with water, it is clear that if this view is correct, vegetable protoplasm must be fed in a very different way from animal, and on very different materials.
Even in the higher flowering plants, in which the processes of the absorption of substances from the environment has been most fully studied, there is a stage in their life in which the nutritive processes approximate very closely to those of the group last mentioned.
Identity of the Food of Animals and Plants.rt is evidently to the actual seats of consumption of food, and of consequent nutrition and increase of living substance, that we should turn when we wish to inquire what are the nutritive materials of plants.
The cell-walls of plants render the entry of solid material into the organism impossible.
Moreover, the stationary habit of plants, and the almost total absence of locomotion, makes it impossible for them to seek their food.
The probability is that this mechanism is to be found in green plants in the leavesat any rate there is a certain body of evidence pointing in this direction.
The nitrogen of the atmosphere is not called into requisition, except by a few plants and under special conditions, as will be explained later.
The power of green plants, not even specialized in any of these directions, to absorb certain carbohydrates, particularly sugars, from the soil was demonstrated by Acton in 1889.
It was formerly the custom to regard as parasites all those pants which inserted roots or root-like organs into the tissues of other plants and absorbed the contents of the latter.
Mycorhizas.The most interesting cases, however, in which Fungi form symbiotic relationships with green plants have been discovered in connection with forest trees.
The plants showing it are not all forest trees, hut include also some Pteridophytes and some of the prothallia of the Ferns, Club-mosses, Liverworts and Horsetails.
From the outer cortical myceliuni, again, branches pass through the epidermis and grow out in the soil, In stich cases the roots of the plants are usuall) found spreading in soils which contain a large amount of humus, or decaying vegetable matter.
Each species of green plant may form a mycorhiza with two or three different Fungi, and a single species of Fungus may enter into symbiosis with several green plants.
Fixation of Nitrogen.Another, and perhaps an even more important, instance of symbiotic association has come to the front during the same period, it is an alliance between the plants of the Natural Order Leguminosae and certain bacterium-like forms which find a home within the tissues of their roots.
Long ago the view that this gas might be the source of the combined nitrogen found in different forms within the plant, was critically examined, particularly by Boussingault, and later by Lawes and Gilbert and by Pugh, and it was ascertained to be erroneous, the plants only taking nitrogen into their substance when it is presented to their roots in the form of nitrates of various metals, or compounds of ammonia.
If experimental plants are grown in ster1lized soil, these swellings do not appear, and the plant can then use no atmospheric nitrogen.
When the root dies later such of these as remain are discharged into the soil, and are then ready to infect new plants.
The enzymes which act upon glucosides are many; the best known are emul sin and myrosin, which split up respectively amygdalin, the special glucoside of certain plants of the Rosaceae; and sinfgrin, which has a wide distribution among those of the Cruciferae.
It is not quite certain whether a true pepsin exists in plants, but many trypsins have been discovered, and one form of erepsin, at least, is very widespread.
Among the trypsins we have the pa pain of the Papaw fruit (Carica Papaya), the bromelin of the Pine-apple, and the enzymes present in many germinating seeds, in the seedlings of several plants, and in other parts.
Another enzyme, rennet, which in the animal body is proteolytic, is frequently met with in plants, but its function has not been ascertained.
Oxidases.Another class of enzymes has been discovered in both animals and plants, but they do not apparently take any part in digestion.
This property of living substance can be proved in the case of the cells of the higher plants, but it is especially prominent in many of the more lowly organisms, such as the Bacteria.
There is some evidence pointing to the existence of this power in the cells of the higher plants.
Again, we have evidence of the power of plants to avail themselves of the heat rays.
The various electrical phenomena of plants also are obscure.
Certain plants possess another source of energy which is common to them and the animal world.
Such a source is commonly met with among the Fungi, the insectivorous plants, and such of the higher plants as have a saprophytic habit.
This source is not, however, anything new, for the elaborated compounds so absorbed have been primarily constructed by other plants through the mechanism which has just been described.
Growth is always going on in plants while they are alive.
In the lowliest plants growth may be co-extensive with the plantbody; in all plants of any considerable size, however, it is localized in particular regions, and in them it is associated with the formation of new protoplasts or cells.
(4) The cell must have a certain temperature, for the activity of a protoplast is only possible within certain limits, which differ in the case of different plants.
Setting aside other susceptibilities, we have evidence that most plants are sensitive to all these.
Many instances might be given of appreciation of and response to other changes in the environment by the growing parts of plants; among them we may mention the opening and closing of flowers during the days of their expansion.
Other and older plants give evidence of the same perception, though they do not respond all in the same way.
The leaves and leaflets of many plants, eg.
A peculiar sensitiveness is manifested by the leaves of the socalled insectivorous plants.
The differentiation of the plants substance so indicated is, however, physiological only; there is no histological difference between the cells of these regions that can be associated with the several properties they possess.
The response made by the adult parts of plants, to which reference has been made, is brought about by a mechanism similar in nature though rather differently applied.
Nor is it only in growing organs that the rhythm can be observed, for many plants exhibit it during a much longer period than that of growth.
AuTH0RITIE5.Sachs, Lectures on the Physiology of Plants, translated by Marshall Ward; Vines, Lectures on the Physiology of Plants; Pfeffer, The Physiology of Plants, trans.
by Moor; Darwin and Acton, Practical Physiology of Plants; Davenport, C.B., Experimental Morphology, vols.
PATHOLOGY OF PLANTS
41UT6V, plant), comprises our knowledge of the symptoms, course, causes and remedies of the maladies which threaten the life of plants, or which result in abnormalities of structure that are regarded, whether directly injurious or not to life, as unsightly or undesirable.
Hales (1727I 733) discussed the rotting of wounds, cankers, &c., but much had to be done with the microscope before any real progress was possible, and it is easily intelligible that until the theory of nutrition of the higher plants had been founded by the work of Ingenhouss, Priestley and De Saussure, the way was not even prepared for accurate knowledge of cryptogamic parasites and the diseases they induce.
It was not till De Bary (1866) made known the true nature of parasitic Fungi, based on his researches between 1853-1863, that the vast domain of epidemic diseases of plants was opened up to fruitful investigation, and such modern treatises as those of Frank (1880 and L895), Sorauer (1886), Kirchner (1890), were gradually made possible.
In plants, however, the symptoms of disease are apt to exhibit themselves in a very general manner.
The yellowing and subsequent casting of leaves, for instance, is a very general symptom of disease in plants, and may be induced by drought, extremes of temperature, insufficient or excessive illumination, excess of water at the roots, the action of parasitic Fungi, insects, worms, &c., or of poisonous gases, and so forth; and extreme caution is necessary in.
For instance, a Fungus epidemic is impossible unless the climatic conditions are such as to favor the dispersal and germination of the spores; and when plants are killed off owi~ig to the supersaturation of the soil with water, it is by no means obvious whether the excess of water and dissolved materials, or the exclusion of oxygen from the root-hairs, or the lowering of the temperature, or the accumulation of foul products of decomposition should be put into the foreground.
Many maladies of plants are traceable to the chemical composition of soilse.g.
Turning to the non-material external agents, probably no factor, are more responsible for ill-health in plants than temperature anc light.
in greenhouses where plants requiring very different optimum temperatures and illumination are kept together.
Equally disastrous are those climatic or seasonal changes which involve temperatures in themselves not excessive but in wrong sequence; how many more useful plants could be grown in the open in the United Kingdom if the deceptively mild springs were not so often followed by frosts in May and June!
All chlorophyll plants require light, but in very different degrees, as exemplified even in the United Kingdom by the shade-bearing beech and yew contrasted with the light-demanding larch and birch; and as with temperature so with light, every plant and even every organ has its optimum of illumination.
The drawn or etiolated condition of over-shaded plants is a case in point, though here again the soft, watery plant often really succumbs to other disease agentse.g.
It should be remembered that a single complete defoliation of a herbaceous annual may so incapacitate the assimilation that no stores are available for seeds, tubers, &c., for another year, or at most so little that feeble plants only come up. In the case of a tree matters run somewhat differently; most large trees in full foliage have far more assimilatory surface than is immediately necessary, and if the injury is confined to a single year it may be a small event in the life of the tree, but if repeated the cambium, bud-stores and fruiting may all suffer.
Plants as agents of damage and disease may be divided into those larger forms which as weeds, epiphytes and so forth, do injury by dominating and shading more delicate species, or by gradually exhausting the soil, &c., and true parasites which actually live on and in the tissues of the plants.
Some very curious details are observable in these cases of malformation, For instance, the Aecidium eta/mum first referred to causes the new shoots to differ in direction, duration and arrangement, and even shape of foliage leaves from the normal; and the shoots of Euphorbia infected with the aecidia of Uromyces Pisi depart so much from the normal in appearance that the attacked plants have been taken for a different species.
Irritation and hypertrophy of cells are common signs of the presence of parasites, as ovinced by the numerous malformations, galls, witches-brooms, &c., on diseased plants.
If the attack of a parasite is met by the formation of some substance in the protoplasm which is chemo- tactically repulsive to the invader, it may be totally incapable of penetrating the cell, even though equipped with a whole armoury of cytases, diastatic and other enzymes, and poisons which would easily overcome the more passive resistances offered by mere cell-walls and cell-contents of other plants, the protoplasm of which forms bodies chemotactically attractive to the Fungus.
The procedure consists in most cases in spraying the affected plants with poisonous solutions or emulsions, or in (lusting them with fungicidal or insecticidal powders, or applying the fumes of lethal gases.
Frost-cracks, scorching of bark by sun and fire, &c., anc wounds due to plants which entwine, pierce or otherwise materially injure trees, &c., on a large scale.
They are due to hypertrophy of young tissues, which may undergo profound alterations subsequently, and occur on all parts of the plants.
The extraordinary forms, colors and textures of the true galls have always formed some of the most interesting of biological questions, for not only is there definite co-operation I between a given species of insect and of plant, as shown by the facts that the same insect may induce galls of different kinds on different plants or organs, while different insects induce different galls on the same plante.g.
The nodules on the roots of leguminous plants are induced by the presence of a minute organism now known to do no injury to the plant.
Nodules due to eel-worms (Nematodes) are produced on numerous classes of plants, and frequently result in great losses-e.g.
Conditions of hyper-turgescence are common in herbaceous plants in wet seasons, or when overcrowded and in situations too moist for them.
Comparable with these cases is that of Cuckoo-spit, due to the juices sucked out by Aphrop/ttkora~ on herbaceous plants of all kinds.
This sketch of an enormous subject shuws us that the pathology of plants is a special department of the study of variations which threaten injury to the plant, and passes imperceptibly into the study of variations in general.
of tke Fungi, &c. (1887); Frank, Die Krankh-eiten der Fflanzen (1895-1896); Sorauer, Handbuch der Pflanzenkrankheiten (i9o6); Ward, Disease in Plants (1901).
I; Richards, The Respiration of Wounded Plants, Ann.
531; and The Evolution of Heat by Wounded Plants, Ann.
Spraying, &c.See Lodeman, The Spraying of Plants (1896), and numerous references in the publications of U.S. Agricultural Department, Zeitschr.
Pflanzenkrankheiten, the Gardeners Chronicle, &c. Etiolation, &c.Pfeffer, Physiology of Plants, and other works on physiology.
2 Warming, Oecology of Plants (Oxford, 1909).
The former is concerned with the division of the earths surface into major districts characterized by particular plants or taxonomic groups of plants, with the subdivision of these floristic districts, and with the geographical distribution (both past and present) of the various taxonomic units, such as species, genera, and families.
Geographical FactorsGeographical position determines the particular species of plants which grow in any particular locality.
Biological FactorsThese include the reactions of plants and animals on the habitat.
The influence of man on plants and vegetation is also a biological factor, which is frequently ignored as such, and treated as if it were a thing apart.
This is due to a lack of precise knowledge of the various habitat factors and also of the responses made by plants to these factors.
Obviously no more than this is possible until physiologists are able to state much more precisely than at present what is the influence of common salt on the plants of salt-marshes, of the action of calcium carbonate on plants of calcareous soils, and of the action of humous compounds on plants of fens and peat moors.
Ecological Classes.Many attempts have been made to divide plants and plant communities into classes depending on habitat factors.
Warming included plants of peat-bogs among his hydrophytes.
Xerophytes.These are plants which live in very dry places, where the substratum has less than 10% of water.
Ha-lophytes.These are plants living in situations where the substratum contains a high proportion of sodium chloride.
Mesophytes.-These are plants which live in localities which are neither specially dry nor specially wet nor specially salty.
The criticisms were directed chiefly to the inclusion of sand dune plants among halophytes, to the exclusion of halophytes from xerophytes, to the inclusion of bog xerophytes among hydrophytes, to the inclusion of all conifers among xerophytes and of all deciduous trees among mesophytes, and to the group of mesophytes in general.
A soil may be physically wet; but if the plants absorb the water only with difficulty, as in a salt marsh, then the soil is, as regards plants, physiologically dry.
Schimper used the term xerophytes to include plants which live in soils which are physiologically dry, and the term hygrophytes those which live in soils which are physiologically wet or damp. Schimper recognized that the two classes are connected by transitional forms, and that it is useless to attempt to give the matter a statistical basis.
Such plants, which comprise the b ~eat majority of the species of the central European flora, ~himper termed tropophytes.
Ilydrophytes.These include plants of the plankton, or micro- W
Helophytes.These are marsh plants which normally have ii, leir roots in soaking soil but whose branches and foliage are more less aerial.
arsh plants and land plants; and it seems equally obvious that F
Oxylophytes.These plants, sometimes spoken of as bog 1(
~rphytes, grow in soils which contain an abundance of free imous compounds, and include plants which grow on fens and le .oors.
Psychrophytes.These include the plants which grow on the lv ild soils of subniveal and polar districts.
Halo phytes.These are plants which grow on saline soils.
Lithophytes.These are plants which grow on true rock, it not on the loose soil covering rock, even though this may W
Psammophytes.These are plants which grow on sand and al avel.
Plants of sand-dunes, whether in maritime or inland e.
calities, are psammophytes, as well as plants (such as Cd7luna U:
Eremophytes.Under this term, are placed plants of deserts rid steppes.
Psilophytes.I-Iere are placed plants found in savannah Igetation, viz.
Many plants of peaty soils e sclerophylious.
Thus, associ- 1~e] ions of Agropyrum (Triticum) junceum, of Carex arenaria, of ~ ~nmophila (Psamma) arenaria, and of other plants occur on sa rid dunes: the associations are related by the general identity ph the habitat conditions, namely, the physiological dryness f d the loose soil; but they are separated by differences in f~1
In the present state of knowledge, however, this can only be done in a very meagre fashion; as the effect of habitat factors on plants is but little understood as yet either by physiologists or ecologists.
Hydroplzytes and hemi-hydrophytes (aquatic plants).Of marine hydrophytes, there are, in this country, only the grass-wracks (Zostera marina and Z.
nana) among the higher plants.
Although many plants typical of fresh water are able to grow also in brackish water, there are only a few species which appear to be quite confined to the latter habitats in this country.
In freshwater lakes and ponds, especially if the water is stagnant, aquatic plants are abundant.
Aquatic plants with submerged and floating leaves: Glyceria fluitans, Ranunculus peltatus, Nymphaea (Nuphar) - lutea, Callitriche stagnalis, Potamogeton polygonifolius.
Aquatic plants with submerged leaves and erect leaves or stems:
In many aquatic plants, the endosperm of the seed is absent or very scanty.
Chloroplastids are frequently present in the epidermal cells, as in some shade plants.
Very few aquatic plants are pollinated under water, but this is wellknown to occur in species of Zostera and of Naias.
In such plants, the pollen grains are sometimes fihiform and not spherical in shape.
In the case of aquatic plants with aerial flowers, the latter obey the ordinary laws of pollination.
Insectivorous species occur among aquatic plants; e.g.
The same plants have sometimes a superficial root system in addition, and are thus able to utilize immediately the water from rain showers and perhaps also from dew, as Volkensl maintains.
Root-hairs give an enlarged superficial area to the roots of plants, and thus are related to the procuring of water.
Cactaceous and Crassulaceous plants, may be succulent, i.e.
Switch plants, such as Retama Retam and broom (Cytisus scoparius), have reduced leaves and some assimilating tissue in their stems; and stomata occur in grooves on the stem.
In cushion plants the leaves are very small, very close together, and the low habit is protective against winds.
The coriaceous leaves of sclerophyllous plants also, to some extent, are similarly protective.
Halo phytes, or plants which live in saline soils, have xerophytic adaptations.
British salt marshes furnish few instances of spiny plants, though such occur occasionally on the inland salt marshesof continental districts.
At one time, such plants were probably of more general occurrence: now they have been extirpated in the intermediate localities, chiefly owing to the cultivation of the land in these places by man.
The effect of common salt on the metabolism of plants is not understood.
Lesagef has shown that the height of certain plants is decreased by cultivation in a saline soil, and that the leaves of iLesage, Recherches exphrimentales sur les modifications de, feuilles chez les plantes maritimes, in Rev. gen.
ii plants under such conditions become smaller and more succulent.
On the other hand, some plants did not respond to the action of common salt, whilst others were killed.
Related to the physiological drought, such plants possess some xerophytic characters; and, related to the physical wetness, the plants possess the aeration channels.
The occurrence of xerophytic characters in plants of this type has given rise to.
With regard to the occurrence of plants, such as Juncus effusus, which possess xerophytic characters and yet live in situations which are not ordinarily of marked physiological dryness, it should be remembered that such habitats are liable to occasional physical drought; and a plant must eventually succumb if it is not adapted to the extreme conditions of its habitat.
The xerophytic characters being present, it is not surprising that many marsh plants, like Juncus effusus and Iris pseudacorus, are able to survive in dry situations, such as banks and even garden rockeries.
Hygrophytes.Living, as these plants do, under medium conditions as regards soil, moisture and climate, they exhibit no characters which are markedly xerophytic or hydrophytic. Hence, such plants are frequently termed mesophytes.
Assimilation goes on during the whole year, except during periods of frost or when the plants are buried by snow.
An interesting special case of hygrophytes is seen with regard to plants which live in the shade of forests.
Such plants have been termed scioplfytes.
bog xerophytes), or that the physical drought of summer is unfavourable to shade-loving plants.
The effect of lime on plants is less understood even than the effect of common salt.
The following plants, in England, are calcifuge: Lastraea Oreopteris, Holcus niollis, Carex ech-inala, Spergula arvensis, Polygala serpyllacea, Cytisu~
Other plants occur indifferently both on calcareous and on non-calcareous soils.
It is sometimes said that lime acts as a poison on some plants and not on others, and sometimes that it is the physiological dryness of calcareous soils that is the important factor.
Further, no theory of calciolous and calcifugous plants can be regarded as satisfactory which fails to account for the fact that both kinds of plants occur among aquatic as well as among terrestrial plants.
Schimper (1903: 102) thinks that in the case of aquatic plants, the difference must depend on the amount of lime in the water, for the physical nature of the substratum is the same in each case.
Again, acidic humus does not form in calcareous soils; and hence one does not expect to find plants characteristic of acidic peat or humus on calcareous soils.
It would therefore be curious if it were proved that lime acts on plants as a poison.
It is said that some plants may be calcicoles in one geographical district and not in another.
However, until more is known of the exact chemical composition of naturalas contrasted with agriculturalsoils, and until more is known of the physiological effects of lime, it is impossible to decide the vexed question of the relation of limeloving and lime-shunning plants to the presence or absence of calcium carbonate in the soil.
CYTOLOGY OF PLANTS
The cell theory so far as it relates to plants was established by Schleiden in 1838.
He showed that all the organs of plants are built up of cells, that the plant embryo originates from a single cell, and that the physiological activities of the plant are dependent upon the individual activities of these vital units.
It is true that in the unicellular plants all the vital activities are performed by a single cell, but in the multicellular plants there is a more or less highly developed differentiation of physiological activity giving rise to different tissues or groups of cells, each with a special function.
Protoplasmic Movements.In the cells of many plants the cytoplasm frequently exhibits movements of circulation or rotation.
The chloroplasts increase in number by division., which takes place in higher plants when they have attained a certain size, independent of the division.
some plants of changing their position in the cell under the stimulus of a variation in the intensity of the light rays which fall upon them.
Substances contained in the Protoplastn.Starch may be found in the chlorophyll bodies in the form of minute granules as the first visible product of the assimilation of carbon dioxide, and it occurs in large quantities as a reserve food material in the cells of various parts of plants.
In the higher plants the structures which have been often described as centrosomes are too indefinite in their constitution.
plants do not appear to be permanent organs of the cell.
The spindle arises partly from the cytoplasm, partly from the nucleus, or it may be derived entirely from the nucleusintranuclear spindleas occurs in many of the lower plants (Fungi, &c.).
The formation of the spindle differs in details in different plants.
We know very little of the details of reduction in the lower plants, but it probably occurs at some stage in the life history of all plants in which sexual nuclear fusion takes place.
Cell Division.With the exception of a few plants among the Thallophytes, which consist of a single multinucleate cell, Caulerpa, Vaucheria, &c., the division of the nucleus is followed by the division of the cell either at once, in uninucleate cells, or after a certain number of nuclear divisions, in multinucleate cells.
In the higher plants, after the separation of the daughter nuclei, minute granular swellingc appear, in the equatorial region, on the connecting fibres which still persist between the two nuclei, to form what is called the cell-plate.
In a few cases both among the higher and the lower plants, of which the formation of spores in the ascus is a typical example, new cells are formed by the aggregation of portions of the cytoplasm around the nuclei which become delimited from the rest of the cell iontents by a membrane.
Cell Membrane.The membrane which surrounds the protoplasts in the majority of plants is typically composed of cellulose, together with a number of other substances which are known as pectic compounds.
~ ------s In many of the lower d- ~ - ~ -~ d plants the fusing cells ~ 9
the lower plants and in - t all hicher plants there is a difference in size in the (From Wilson.
The eggcell or oosphere is a large cell containing a single large nucleus, and in the green plants the rudiments of plastids.
In plants with multinucleate cells, such as Albugo, Peronospora and Vaucheria, it is usually a uninucleate cell differentiated by separation of the nuclei from a multinucleate cell, but in Albugo bliti it is multinucleate, and in Sphaero plea it may contain more than one nucleus.
It was at one time thought that the centrosomes played an important part in the fertilization of plants, but recent researches seem to indicate that this is not so.
The strongest direct evidence seems to be that the nuclear substances are the only parts of the cells which are always equivalent in quantity, and that in the higher plants and animals the male organ or spermatozoid is composed almost entirely of the nucleus, and that the male nucleus is carried into the female cell without a particle of cytoplasm.i Since, however, the nucleus of the female cell is always accompanied by a larger or smaller quantity of cytoplasm, and that in a large majority of the power plants and animals the male cell also contains cytoplasm, it cannot yet be definitely stated that the cytoplasm does not play some part in the process.
Rosenberg (1909) adduces evidence fox the existence of chromosomes or prochromosomes in resting nuclei in a large number of plants, but most observers consider that the chromosomes during the resting stage become completely resolved into a nuclear network in which no trace of the original chromosomes can be seen.
The researches of the last twenty years have shown that the structure of the nucleus and the phenomena of nuclear division in these lower forms conforms in all essential details to those in the higher plants.
Tissues.The component parts of the tissues of which plants are composed may consist of but slightly modified cells with copious protoplasmic contents, or of cells which have been modified in various ways to perform their several functions.
The formation of the conducting tubes or secretory sacs which occur in all parts of the higher plants is due either to the elongation of single cells or to the fusion of cells together in rows by the absorption of the cell-walls separating them.
Protoplasmic Continuity.Except in the unicellular plants the cell is not an independent unit.
Apart from their dependence in various ways upon neighboring cells, the protoplasts of all plants are probably connected together by fine strands of protoplasm which pass through the cell-wall (Tangl, Russow, Gardiner, Kienitz-Gerloff and others) ___________
The threads vary in size in different plants.
v.; The Cell and some of its Constituent Structures, Science Progress (1897); Farmer and Moore, On the Melotic Phase in Animals and Plants, Quart.
MORPHOLOGY OF PLANTS
The term morphology, which was introduced into science by Goethe (1817), designates, in the first place, the study of the form and composition of the body and of the parts of which the body may consist; secondly, the relations of the parts of the same body; thirdly, the comparison of the bodies or parts of the bodies of plants of different kinds; fourthly, the study of the development of the body and of its parts (ontogeny); fifthly, the investigation of the historical origin and descent of the body and its parts (phylogeny); and, lastly, the consideration of the relation of the parts of the body to their various functions, a study that is known as organography.
The earliest scientific result of the study of plants was the recognition of the fact that the various parts of the body are associated with the performance of different kinds of physiological work; that they are, in fact, organs discharging special functions.
The origin of the organography of the present day may be traced back to Aristotle, who described the parts of plants as organs, though very simple ones.
Pure Morphology.Thus it became apparent that the mans and various organs of plants are, for the most part, different forms of a small number of members of the body, which have been distinguished as follows, without any reference to function.
The tisallus (thallome) is a plant-body which is not differentiated into the members root, stem and leaf; it is the morphologically simplest body, such as is of common occurrence in the lower plants (e~.
However, they belong respectively to two different forms in the life-history of the plants; the leaves of the mosses are borne by the gametophyte, those of the club-mosses by the sporophyte.
Another effect is that different degrees of homology have to be recognized, just as there are different degrees of relationship or affinity between individual plants.
The leaf of the higher plants will be taken as the illustrative case because it is the most plastic of the members, the one, that is, which presents the greatest variety of adaptations, and because it has been most thoroughly studied.
The evolution of higher from lower plants, it is generally assumed, has proceeded by variation.
Exceptions to this attitude are Lamarck, who speaks with regard to animals (but not to plants!) of f la composition croissante de lorganisation (Philoso p/lie zoologique, t.
There is every reason to believe that plants are as irritable to varying external conditions as they are to light or to gravity.
In illustration of the indirect response, the evolution of the Bryophyta and of more highly organized plants may be briefly considered.
It is generally admitted that life originated in water, and that the earliest plants were Algae.
The study of existing Algae, that is of plants that have continued to live in water, shows that under these conditions no high degree of organization has been reached, though some of them have attained gigantic dimensions.
For instance, the animal traps of carnivorous plants (Drosera, Nepenihes, &c.) did not, presumably, originate as such; they began as organs of quite another kind which became adapted to their present function in consequence of animals having been accidentally caught.
Moreover, had the evolution of plants proceeded along the line of adaptation, the vegetable kingdom could not be subdivided, as it is, into the morphological groups Thallophyta, Bryophyta, Pteridophyta, Phanerogamia, but only into physiological groups, Xerophyta, Hygrophyta, Tropophyta, &c.
LITERATURE.AS the scope of this article limits it to the general principles of the morphology of plants, comparatively few facts have been adduced.
Full morphological and organographical details are given in the articles on the various groups of plants, such as those on the Algae, Bryophyta, Pteridophyta, Angiosperms, Gymnosperms, &c. The following works may also be consulted:
DISTRIBUTION OF PLANTS
Common experience shows that temperature is the most important condition which controls the distribution of plants.
The cardoon and milk thistle, both European plants, cover tracts of country in South America with impenetrable thickets in which both man and beast may be hopelessly lost.
We are compelled to take into account the actual affinity of the plants inhabiting them.
A transformation which is sometimes rapid, sometimes slow, but always continuous, is wrought by the reciprocal action of the innate variability of plants and of the variability of the external factors.
This change is due partly to the migrations of plants, but chiefly to a transformation of the plants covering the earth.
the descendants, and constitute the so-called adaptations in which the external factors acting on the plants are reflected.
This is easy to happen with plants dependent on insects for their fertilization.
The actual and past distribution of plants must obviously be controlled by the facts of physical geography.
Herbaceous plants are rare and mostly epiphytic.
If we take with Drude the number of known families of flowering plants at 240, 92 are generally dispersed, 17 are more restricted, while the remainder are either dominant in or peculiar to separate regions.
Both were in turn replaced by the Lower Mesozoic flora, which again is thought to have had its birth in the hypothetical Gondwana land, and in which Gymnosperms played the leading part formerly taken by vascular Cryptogams. The abundance of Cycadean plants is one of its most striking features.
As Clement Reid remarked: World-wide floras, such as seem to characterize some of the older periods, have ceased to be, and plants are distributed more markedly according to geographical provinces and in climatic zones.
Sequoia and the tulip-tree still remain; figs are abundant; laurels are represented by Sassafras and camphor; herbaceous plants (Ranunculaceae, Cruciferae, Umbelliferae) are present, though, as might be expected, only fragmentarily preserved.
The Pliocene flora found refuges in favored localities from which at its close the lowlands were restocked while the arctic plants were left behind on the mountains.
It results that besides a horizontal distribution of plants, there is also an altitudinal: a fact of cardinal importance, the first observation of which has been attributed to Tournefort.
Speaking generally, all plants tend to exhaust particular constituents of the soil on which they grow.
Yet in 1886 Treub found that it was beginning to cover itself again with plants, including eleven species of ferns; but the nearest source of supply was 10 m.
The seeds of West Indian plants are thrown on the western shores of the British Isles, and as they are capable of germination, the species are only prevented from establishing themselves by an uncongenial climate.
Rivers bring down the plants of the upper levels of their basins to the lower: thus species characteristic of the chalk are found on the banks of the Thames near London.
Seeds are carried in soil adhering to their feet and plumage, and aquatic plants have in consequence for the most part an exceptionally wide range.
It equally fails for plants.
If we turn to herbaceous plants, Hemsley has pointed out that of the thirteen genera of Ranunculaceae in California, eleven are British.
de Candolle, however, points out, exclusive reliance on this may be misleading unless we also take into account the character and affinities of the plants dealt with (Geogr.
The Arctic-Alpine sub-region consists of races of plants belonging originally to the general flora, and recruited by subsequent additrons, which have been specialized in low stature and great capacity of endurance to survive long dormant periods, sometimes even unbroken in successive years by the transitory activity of the brief summer.
Arctic plants make their brief growth and flower at a temperature little above freezing-point, and are dependent for their heat on the direct rays of the sun.