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POPULAR SCIENCE REVIEW. 
oarbon by plants, the light absorbed by the leaves is transformed into so 
much mechanical or chemical work ; and if we further admit that the plant 
by itself is unable to dissociate the carbon and oxygen of carbonic acid, and 
that this dissociation is only possible under the influence of light, we must 
also admit that the force required to produce such a result is necessarily 
greater than the force which determines the combustion of the carbon, and 
•consequently that it is greater than the mechanical work represented by the 
heat developed under these conditions. — Vide Comptes Rendus, Feb. 17. 
Ancdysis of the Tissues of Plants. — The many ditficulties in the way have 
hitherto prevented a satisfactory chemical qualitative or quantitative ex- 
amination of plant tissues. These difficulties have at last, however, been 
overcome by MM. Fremy and Terreil, who have just published a memoir 
describing the methods and stating their results. They divide the woody 
portion into three separate classes, and give the following account of their 
chemical qualities. The first portion of the wood is not to be confounded 
with any other ligneous tissue, for it is insoluble in even concentrated sul- 
phuric acid, and it is characterised by these reactions : chlorine water first 
transforms it into a yellow acid, and then dissolves it, nitric acid acts simi- 
larly, but even concentrated caustic potass does not dissolve it. This part 
is termed the ligneous cuticle. It is not identical with the cuticle of the 
leaves, but it has many analogies with it. It may be at once distinguished 
by its complete insolubility in concentrated sulphuric acid, and its ready 
solubility in chlorine water. The second portion of the woody tissue is that 
which M. Pay en has designated under the name incrusting substance. It is 
most likely found in the interior of the fibres and cells. This substance is 
at once identified by its ready solubility in sulphuric acid, which it blackens, 
and by its insolubility in chlorine water. The third part of the woody 
tissue is the cellidosic part. When this is pure it dissolves — without giving 
any colour — in concentrated sulphuric acid, and produces a liquid which is 
not precipitated by water, and is with difficulty acted on by nitric acid. 
We have shown how the French chemists make a qualitative analysis of 
these constituents of woody tissue. For the quantitative method we must 
refer readers to the original paper. — Vide li Institut, March 11. 
The Venation of the Umhelliferce. — The paper which was lately read before 
the Microscopical Society by Mr. T. Gorham, is one which is of much 
interest, and which shows what a large field remains for work, even in a 
subject like botany, which has been- so much and so carefully studied. 
Mr. Gorham, by using a low microscopic power, has thrown considerable 
light on the arrangement of the nervures of the leaves of umbelliferous plants, 
and he formulates the following conclusions : — 1. That the distribution of 
the veins in Umbelliferse is very variable in different species, but constant 
and highly characteristic in each species. 2. That many of the leaves of 
this order have a venation like that in other leaves, and may be classified 
with them; but that a considerable number of them, on the other hand, 
have a kind of venation peculiar to themselves, which does not find a place 
under any of the divisions that have heretofore existed. 3. That this pecu- 
liarity consists in the existence of a vein at the very edge of the leaf itself, 
and which, more or less, entirely fringes its whole margin. 4. That this 
marginal vein is to be found certainly in one half, if not more, of the species 
