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.
Bacteria (see BACTERIOLOGY) and Cyanophyceae (see ALGAE), which are often grouped together as Schizophyta, are from points of view of both structure and reproduction extremely simple organisms, and stand apart from the remaining groups, which are presumed to have originated directly or indirectly from the Flagellatae, a group of unicellular aquatic organisms combining animal and plant characteristics which may be regarded as the starting-point of unicellular Thallophytes on the one hand and of the Protozoa on the other.
A, Cell (individual) of the unicellular Green Alga Pleurococcus, as an example of an undifferentiated autonomous assimilating cell.
None of the existing Red Seaweeds (Rhodophyceae) has a unicellular body.
This may have a radial stem-like organization, a central cell-thread giving off from every side a number of short sometimes unicellular branches, which together form a cortex round the central thread, the whole structure having a cylindrical form which only branches when one of the short cell-branches from the central thread grows out beyond the general surface and forms in its turn a new central thread, from whose cells arise new short branches.
What little differentiation can be found to exist in the protoplasm of the simple unicellular organism shows the importance of an adequate water-supply, and indeed, the dependence of life upon it.
Pythium in seedlingsor to a poison diffusing from cell to cell; in the case of unicellular plantse.g.
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 Continuity.Except in the unicellular plants the cell is not an independent unit.
Qutun), the most important of the vegetable fibres of the world, consisting of unicellular hairs which occur attached to the seeds of various species of plants of the genus Gossypium, belonging to the Mallow order (Malvaceae).
In it are, moreover, enclosed unicellular glands pouring their highly refracting contents, of a more or less rod-like shape, directly to the exterior.
Haeckel himself, with his pupil MikluchoMaclay, had in the meantime made studies on the growth from the egg of Sponges - studies which resulted in the complete separation of the unicellular or equicellular Protozoa from the Sponges, hitherto confounded with them.
From the histological examination of tumour cells there is no evidence to show that they resemble the protozoal unicellular organisms in occasionally passing through a sexual process of reproduction, i.e.
A great variety of forms were described by other observers, but they were not separated as a class from the unicellular organisms (Protozoa) with which they usually occur, until the appearance of C. G.
LICHENS, in botany, compound or dual organisms each consisting of an association of a higher fungus, with a usually unicellular, sometimes filamentous, alga.
The spores themselves may be unicellular without a septum or multicellular with one or more septa.
Spores unicellular, parallel-multicellular or muriform, usually colourless, cross-walls usually thin.
Fungus, a mushroom), the botanical name covering in the broad sense all the lower cellular Cryptogams devoid of chlorophyll, which arise from spores, and the thallus of which is either unicellular or composed of branched or unbranched tubes or cell-filaments (hyphae) with apical growth, or of more or less complex wefted sheets or tissue-like masses of such (mycelium).
Physiologically, any cell or group of cells separated off from a hypha or unicellular fungus, and capable of itself growing out - germinating - to reproduce the fungus, is a spore; but it is evident that so wide a definition does not exclude the ordinary vegetative cells of sprouting fungi, such as yeasts, or small sclerotium like cell-aggregates of forms like Coniothecium.
Alga-like fungi with unicellular thallus and well-marked sexual organs.
These parasitic and minute, chiefly aquatic, forms may be looked upon as degenerate Oomycetes, since a sexual process and feeble unicellular mycelium occur in some; or they may be regarded as series of primitive forms leading up to higher members.
Analogies have been pointed out between Chytridiaceae and unicellular algae, such as Chlorosphaeraceae, Protococcaceae, "Palmellaceae," &c., some of which are parasitic, and suggestions may be entertained as to possible origin from such algae.
The protoplasm then becomes cut up by a series of clefts into a number of smaller and smaller pieces which are unicellular in Pilobolus, multicellular in Sporodinia.
They are characterized by their unicellular nature, their power of rapid budding, their capacity for fermenting various sugars, and their power of forming endogenous From Strasburger's Lehrbuch der Botanik, by permission of Gustav Fischer.
This very large group of plants is characterized by the possession of a special type of conidiophore - the basidium, which gives its name to the group. The basidium is a unicellular or multicellular structure from which four basidiospores arise as outgrowths; it starts asa binucleate structure, but soon, like the ascus, becomes uninucleate by the fusion of the two nuclei.
The thallus may be unicellular or multicellular.
When unicellular, it may consist of isolated cells, but more commonly the cells are held together in a common jelly (Chroococcaceae) derived from the outer layers of the cell-wall.
In these cases, certain cells of a colony of unicellular plants or of the filaments of multicellular plants enlarge greatly and thicken their wall.
Chlamydomonas sp., unicellular; chr.,chromatophore; p.,pyrenoid; H.
In unicellular forms (Sphaerella) the thallus becomes transformed into a zoosporangium at the reproductive stage.
Before leaving the Chlorophyceae, it should be mentioned that the genus Volvox has been included by some zoologists (Btitschli, for example) among Flagellata; on the other hand, certain green Flagellata, such as Euglena, are included by some botanists (for example, van Tieghem) among unicellular plants.
Of these the first three include multicellular plants, some of them of great size; the last three are unicellular organisms, with little in common with the rest excepting the possession of a brown colouring matter.
The thallus is somewhat spherical and unicellular, exhibiting a distinction between anterior and posterior extremities, and dorsal and ventral surfaces.
The Cryptomonadaceae also are unicellular, and live free or in colonies.
No unicellular Rhodophyceae are known, although a flagellate organism, Rhodomonas, has recently been described as possessed of the same red colouring matter.
These are for the most part long, thin-walled, unicellular and colourless, and arise from the outer cells of the pseudo-cortex, or from the terminal cells of branches when the filaments are free.
The spores of Monospora are by some regarded as unicellular propagula.
Again, many Green Algae - some unicellular, like Sphaerella and Chlamydomonas; some colonial forms, like Volvox and Hormotila: some even filamentous forms, like Ulothrix and Stigeoclonium- are known to pass into a condition resembling that of a Palmella, and might escape identification on this account.
The organisms constituting this plankton are mostly unicellular, of ten aggregated together in colonies, and the remarkable structure which they exhibit has added a new chapter to the story of adaptation to environment.
While some unicellular forms are less than (.
Vegetative body unicellular; spheroidal, cylindrical or spirally twisted; isolated or connected in filamentous or other growth series.
By sensitiveness to chemical substances in their surroundings - a property which is not peculiar to them but is possessed by various unicellular organisms, including motile bacteria.
In Actinians the epithelio-muscular cells of the endoderm are crowded with yellow spherical bodies, which are unicellular plants or Algae, living symbiotically in the tissues of the zooid.