A, Ordinary leaf of Cephalotus.
B, Monstrous leaf with spoon-shaped depression.
Hardly a leaf is visible to the height of one's head; but above, a crown of thick leather-like leaves shuts out the sunlight.
Sarah would say, "Seen one orange leaf, seen 'em all."
She shook like a leaf in a thunderstorm, her warm brown eyes wide and tears streaming down her cheeks.
In other cases the trace passes inwards and joins the central hydrom strand, so that a connected water-conducting system between stem and leaf is established.
A study of the development of the pitcher, especially in the young pitchers of seedling plants, shows that the inflated portion is a development of the midrib of the leaf, while the wings, which are especially well represented in the terrestrial type of pitcher, represent the upper portion of the leaf-blade which has become separated from the lower portion by the tendril; the lid is regarded as representing two leaflets which have become fused.
The centre of the leaf is often occupied by a midrib consisting of several layers of cells.
The leaf-stalks and flowerstalks are traversed by longitudinal air-passages, whose disposition varies in different species.
After another moult the insect passes into the passive nymphal or " pupal " stage, during which it takes no food and rests in some safe hiding-place, such as the soil at the base of its food-plant or the hollow of a leaf-stalk.
The electroscope was used in conjunction with an oil lamp or gas flame.
The title, which is written on the first leaf, and is also in Robert Napier's writing, runs thus: "The Baron of Merchiston his booke of Arithmeticke and Algebra.
Thus any twining plant with a heart-shaped leaf, white and green above and purple beneath, is called by them guaco (R.
The oak in Europe is liable to injury from a great variety of insect enemies: the young wood is attacked by the larvae of the small stag-beetle and several other Coleoptera, and those of the wood-leopard moth, goat moth and other Lepidoptera feed upon it occasionally; the foliage is devoured by innumerable larvae; indeed, it has been stated that half the plant-eating insects of England prey more or less upon the oak, and in some seasons it is difficult to find a leaf perfectly free from their depredations.
They are shrubby plants climbing over surrounding vegetation by means of tendrillike prolongations of the midrib of the leaf beyond the leaf-tip.
The short straight or curved process from the back of the pitcher behind the lid represents the organic apex of the leaf (A in fig.
Insects are attracted to the mouth of the pitcher by a series of glands, yielding a sweet excretion, which occurs on the stem and also on the leaf from the base of the leaf-stalk to the lid and peristome.
Insects, especially running insects, which have followed the track of honey glands upwards from the stem along the leaf, reach the mouth of the pitcher, and in their efforts to sip the attractive marginal glands fall over into the liquid.
The leaf has a broadly sheathing base succeeded by a short stalk bearing the pitcher, which represents a much enlarged midrib with a winglike lamina.
The surface of the leaf, especially the laminar wing, bears glands which in spring exude large glistening dr„ r, s of nectar.
The lid and mouth of the pitcher are brighter coloured than the rest of the leaf, which FIG.
Laymen may read the book of nature, and Man himself is the most important " leaf " in it.
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.
The Mosses and Liverworts include forms with a more or less leaf-like thallus, such as many of the liverworts, and forms in which the plant shows a differentiation into a stem bearing remarkably simple leaves, as in the true mosses.
The Ferns and fern-like plants have on the other hand a well developed independent sporophyte which is differentiated into stem, leaf and root with highly organized internal structure including true vascular bundles.
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.
T, Part of vertical section through blade of typical leaf of Phanerogam.
This differentiation is parallel with that between stem and leaf of the higher plants.
In Caulerpa the imitation of a higher plant by the differentiation of fixing, supporting and assimilating organs (root, stem and leaf) from different branches of the single cell is strikingly complete.
Or the thallus may have a leaf-like form, the branches from the central threads which form the midrib growing out mainly in one plane and forming a lamina, extended right and left of the midrib.
In many cases the cells bordering the leaf are produced into teeth, and very frequently they are thick-walled so as to form a supporting rim.
In a few cases the hydrom strand is continued into the cortex of the stem as a leaf-trace bundle (the anatomically demonstrable trace of the leaf in the stem).
The leaf consists of a central midrib, several cells thick, and two wings, one cell thick.
This bundle is continued down into the cortex of the stem as a leaf-trace, and passing very slowly through the sclernchymatous external cortex and the parenchymatous, starchy internal cortex to join the central cylinder.
These three concentric tissue mantles are evidently formed by the conjoined bases of the leaf traces, each of which is composed of the same three tissues.
In the more highly developed series, the mosses, this last division of labor takes the form of the differentiation of special assimilative organs, the leaves, commonly with a midrib containing elongated cells for the ready removal of the products of assimilation; and in the typical forms with a localized absorptive region, a well-developed hydrom in the axis of the plant, as well as similar hydrom strands in the leaf-midribs, are constantly met with.
Other hairs consist of a chain of cells; others, again, are branched in various ways; while yet others have the form of a flat plate of cells placed parallel to the leaf surface and inserted on a stalk.
2, A), which has distinct upper and lower faces, are placed mainly or exclusively on the lower side of the leaf, where the water vapour that escapes from them, being lighter than air, cannot pass away from the surface 01 the leaf, but remains in contact with it and thus tends to check further transpiration.
In the leaf-blade this sometimes aopears as a layer of thickened subepidermal cells, tht hypoderm, often also as subepidermal bundles of sclerenchymatou~ fibres, or as similar bundles extending right across the leaf from mu epidermis to the other and thus acting as struts.
In the larger veins of the leaf especially in the midrib, in the petiole, and in the young stem, a1 extremely frequent type of mechanical tissue is collenchyma.
As the stele is traced farther upwards it becomes bulkier, as do the successive leaf-bundles which leave it.