Researches in Vegetable Physiology. 231 



ceding summer, and destined to become retransformed wlien it 

 reaches the buds. The proportion, faithfullj represented by 

 a great number of curves, is but slight at the first awakening 

 of vegetation ; it increases gradually up to a certain maximum, 

 in proportion as the vital phenomena acquire more intensity ; 

 and, finally, it diminishes when the young organs, approach- 

 ing the term of their development, are on the verge of suf- 

 ficing for themselves. These facts are therefore perfectly in 

 accordance with such a theory of growth as has been esta- 

 blished by the researches of modern observers. 



The albumen and the mineral salts are successively studied 

 from the same point of view ; and their dissemination in the 

 sap at different heights at the same moment, and at different 

 periods, is exactly governed by the different phases of deve- 

 lopment. 



The second part is devoted to the microscopic examination 

 of the bud. The different substances which are called upon 

 to assist in the development of the young leaf are traced by 

 means of reagents from cell to cell. Two, especially, give 

 origin to detailed observations, namely starch and tannin. 



The dissemination of the former in the different tissues, its 

 transportation through the starchy layers of the fibro-vascular 

 bundles, its disappearance towards the point of vegetation, at 

 the surface of which it speedily reappears as cellulose — all 

 these different phases are taken up step by step ; and here, 

 again, we find a confirmation of all that theory led us to 

 foresee. 



As to tannin, it is developed in all the cells of the bud ; 

 and when once it has made its appearance, it persists there 

 without appreciable change. Its function has greatly embar- 

 rassed M. Schroeder, as he was unable to recognize in it any 

 of the characters of an excrementitial product, properly so 

 called. The fact that it is constantly to be found in the 

 youngest tissues (in which life is most intense) seems to indicate 

 that it is a sort of final product, charged with a still unknown 

 office in the life of the cell. If the true chemical nature of 

 this substance were better known, the solution of the problem 

 would perhaps become easier. 



Certain authors have thought that the course of vegetation 

 in the Agaiics induced a marked exhalation of gaseous ammonia 

 at their surface. M. Sachs mentions the fact in his ' Treatise 

 on Physiology,' but without absolutely affirming it. M. Bor- 

 scow * has undertaken a series of experiments, upon which he 



* Melanges Biologiquea tir& du Bull, de I'Acad. Imp. des Sci. de St.- 

 P^tersb. tome vii. p. \'2\. 



