DECEMBER. 
271 
shall afterwards enter into a detailed account of these two classes of organs, 
which are the elements of all vegetable substances. It is sufficient for the 
present to call these threads by the name of fibres , and the soft spongy matter 
by that of parenchyma. 
As for the green flat blades (l), which are placed along the superior axis, 
it will be easy to recognise in them the same organisation as in the axis itself; 
the only difference is in the proportions of the parenchyma and the fibres. 
You will see in them, detaching itself from the axis, a bundle of fibre, growing 
out to a considerable distance from the point whence it issued. This bundle 
spreads out into a green blade, which is composed of fibres and parenchyma like 
the axis, but that the parenchyma is there more abundant than the fibre, and 
constitutes nearly the whole of it. Observe, besides, that the bundle produced 
by the axis extends down the middle of the green blade, and branches out 
laterally to form this same blade. It also diminishes in width in proportion as 
it lengthens, and throws out upon its side fibres and parenchyma. In order to 
see this arrangement better, take a leaf of the Cherry tree {fig- 2), or of the 
Plum tree, the PeaV tree, or the Oak. 
These green blades are called leaves. The bundle of fibre from which they 
are produced bears the name of footstalk , from the point where it disengages 
itself from the axis to that where it widens, when 
it begins to unfold it takes the name of limb. Now 
you see, in the Wallflower (page 8, fig. 1), there 
is scarcely any footstalk, since the unfolding begins 
almost as soon as the bundle comes out of the 
dally in the upper leaves. But we shall 
see that, among our plants, there are 
half among which the bundle producing 
the leaf remains closely bound together for a con¬ 
siderable length, and forms a perfectly distinct 
footstalk. Plowever, whether the footstalk exist 
or not, the part which spreads out in the blade 
always takes the name of limb. 
The various fibrous ramifications, which are 
projected in the limb of the leaf by the bundle which 
produces them, are calld veins {fig. 2—2, 3). The 
bundle itself, occupying the middle of the length of 
the limb, takes the name of the midrib {fig. 2—1), 
and the fibres which diverge from each side of this 
midrib are called lateral ribs {fig. 2—3). These 
lateral ribs or veins, although very fine in the 
Wallflower, are, nevertheless, visible to the naked 
eye, especially on one of the surfaces of the leaf, 
where they can be seen swerving a little from the Fig.2—Leaf of the Cherry, 
midrib, and showing like it in the limb. 
This limb, besides the succulent dark green matter called parenchyma, 
which in a great measure composes it, and the ramifying veins which serve as 
a sort of framework, is protected by a fine skin, colourless and transparent, 
which covers it on its two surfaces, and which is called epidermis. We shall 
afterwards study this pellicle in its particular structure, and, I can tell you 
beforehand, that it will excite your admiration. Meanwhile, it is easy to prove its 
existence to you, on the young shoots as well as on the leaves, either by means 
of a knife, with which you may easily detach it, or by an oblique tear of the leaf. 
In order to complete the outward examination of the leaf, I must premise 
that its limb offers to our consideration an apex, a base, two edges, and two 
axis, espet 
presently 
nearlv the 
