56 
THE FOLIAGE— AND ITS FUNCTIONS. 
The parenchyma, with it chlorophyl, (green-yellow colouring matter — a term not 
quite arbitrary.) is evidently vascular, admitting the interflow of every fluid or gas 
that is to be subjected to the laborating energy of the foliage. The pores or stomates, 
however placed, whether on the underside only, or on both sides of the leaf-plate, 
seem by their position to prove the existence of a respiratory power. That pores 
exist no person can doubt who possesses a microscope and is able to detach a trans- 
parent scale of the outer integument of a leaf. To dissect the tissue, to detach its 
external membrane, and completely to disclose the position and orifices of the pores, 
demands the skill and apparatus of the practised anatomist; but any ingenious person 
can satisfy himself of the general fact alluded to, though it should appear that our 
utmost powers of observation, aided by legitimate analogy, has not been quite able 
to determine without question or doubt whether the organism of the foliage, with its 
transpiratory system of pores opening to the air, is devoted to the office of expiration, 
inspiration, or of both, connectedly or reciprocally. Of the first-named function we 
are practically assured; for who could doubt, after witnessing the drops of water which 
accumulate upon any broad leaf, lying underneath and in juxta-position with the 
lower surface of a vine leaf, produced in a glazed erection, during the full sunshine, 
at and about the hour of noon ? We mention this leaf, because it is so open to 
general notice ; nevertheless the position of the stomates warrants the transpiratory 
office of almost every variety of leaves. But the phenomenon of the exudation of 
aqueous matter does by no means imply that water alone is exuded ; gases may, and 
do pass through, the pores ; and these are exceedingly varied in their chemical com- 
ponents. But of this more hereafter. The inquiry which immediately presents 
itself is this — Do leaves m-hale ? do they absorb carbonic acid and ammonia from 
the atmosphere ? is there any undoubted fact which can prove to demonstration that 
they possess this attractive power ? Without daring to assert the contrary — on the 
other hand, being inclined by comparative analogy to subscribe to the received 
hypothesis, we are constrained to question the validity of the evidences upon which 
it is founded ; and now hasten to refer to some statements that have very lately 
been made in a public lecture, wherein we read, that — 
" If an acorn be put into the ground it will germinate, and progressively increase 
till it become 'a large oak containing thousands of pounds of charcoal.' This is a 
somewhat bold and delusive assertion, in so far, that the tree does not contain one 
grain of charcoal, properly so called — since it is evident to the most unreflecting, 
that charcoal is a product of the slow combustion or distillation of wood ; it is the 
coke of wood. Ligneous matter is abundant in a tree — a natural compound of oxygen, 
hydrogen, and carbon, or in other words, of three great elements, that can be 
developed under those forms, The mind is grievously mystified by these hazardous 
assertions ; which may be met by the simple fact, that natural productions rarely 
contain any of those substances which are developed in our laboratories. For 
instance, alcohol is a product of sugar, readily obtained, and merely by a change 
among the three elements ; but there is not a particle of real alcohol in sugar, or 
