27G VEGETABLE ORGANOGRAPHY. 



matters, and are then found to become deposits of nutri- 

 ment for a given period or a given part of plants. The 

 organs thus modified are the more important to study, 

 since they perform a considerable part in the nutrition 

 of plants, and often produce phenomena apparently con- 

 tradictory to the progress of the sap. In fact, if it be 

 true, as vegetable physiology appears to demonstrate, 

 that the sap is only elaborated in the foliaceous parts, 

 and only becomes a nourishing juice after this elabora- 

 tion, how can we understand the nutrition of a great 

 number of organs which can receive no action from the 

 foliaceous parts, and which are evidently nourished by 

 the ascending sap ? 



The cellular tissue of several very different organs is 

 capable of being dilated, and of receiving a much larger 

 quantity of water than usual ; it is this which constitutes 

 the ordinary state of the leaves of succulent plants, that 

 of several fleshy roots, that of succulent pericarps called 

 fleshy fruits, that of fleshy spermoderms, &c. 



The nature of the water accumulated in the tissue 

 presents differences, both between one organ and an- 

 other, and one plant and another : thus, the water which 

 swells up the leaves of several Ficoids contains earthy 

 and alkaline salts in solution ; that which is in most 

 fruits contains mucilaginous or saccharine matters, &c. 



The tendency of each organ to a state of anasarca is 

 sometimes constant in the species, sometimes accidental. 

 Thus, the leaves of Ficoids, Crassulaceae, PortulaceaB, 

 Aloes, &c. the stems of the Cacteas, Stapelia, &c, and 

 the perigones oiBUtum, are constantly fleshy. The peri- 

 carps of a great number of plants also present this dis- 

 position in a permanent manner. In all these cases we 

 remark that this state is connected with the total ab- 

 sence of the stomata when it affects fruits, or with their 

 small number when it affects leaves. 





