378 M. Coste on the Formation of Cells. 
Thus, as soon as the demonstration of this identity was appa- 
rently obtained, and, under the influence of this conviction, natu- 
ralists sought for the explanation of so remarkable a phenomenon, 
science seemed to acquire fresh vigour, and all those facts which 
now form the base of phytogeny appeared to emanate from the 
attempts which were made to solve this interesting problem, 
In fact, how could it happen that the same part of a vegetable, 
under the influence of external circumstances, produced organs 
which then appeared so different as a stem, a root, a bud, or a 
leaf? To what structural cause could the possibility of so re- 
markable a metamorphosis be attributed? Such was the idea 
which observers entertained, and which directed their researches 
im the new path opened to them. 
Success speedily crowned their endeavours, and their earhest 
labours in unveiling the true structure of plants led them to the 
important result, that a vegetable, be the complication of its or- 
gans ever so great, 1s essentially nothing more than a collective 
being, composed of an assemblage of vesicles, utricles or cells, 
which are so many living individuals, originally identical, enjoy- 
ing the power of growth, multiplication and capability when oc- 
casion requires of reproducing the plant of which they form the 
constituent materials. If these vesicles, utricles or cells are not 
excited to any further development, they continue simply to form 
part of the tissue of the plant they constitute; or they may be 
absorbed to serve for the nutrition of those cells, which, being 
more advantageously placed, are destined for new transformations : 
but if, on the contrary, the influence of more favourable cireum- 
stances is felt, we then find that their original aptitude is aroused, 
and is called into action under the most varied forms ; without 
however ever exceeding the assigned limits of the species to which 
they belong. 
The original identity of vegetable cells, and the power attri- 
buted to them of beimg transformed in so varied a manner, is 
not an hypothesis created by the necessity of any theory ; it is a 
fact confirmed by experiment, and which can be reproduced at 
pleasure ; but this is not the place for studying the mechanism 
by which such metamorphoses as these are to be accomplished. 
It is sufficient to know at present that vegetable tissue is exclu- 
sively composed of cells, to understand how physiologists, guided 
by analogy, when direct observation had put them in possession 
of this fact, were necessarily led to inquire whether the animal 
organization was not similarly placed as regards structure. 
This problem was much more difficult of solution, for the or- 
gans in animals are capable of attaining so great a degree of 
complication, that it frequently becomes impossible to penetrate 
into their structure as observed in the adult; but if precaution 
