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- 

 raHsts sought for the explanation of so remarkable a phsenomenon, 

 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, 

 tinder 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 

 in the new path opened to them. 



Success speedily crowned their endeavours, and their earliest 

 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, is 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 circum- 

 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 being 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 difiicult 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 



