CELLULAR TISSUE. 27 



serve for the ascent of the unelaborated sap, which, from 

 the roots, spreads throughout all the foKaceous parts of 

 the plant. 



2d. The intercellular passages situated between the 

 cellules of the medullary rays establish the transverse 

 communication of the sap, from the centre to the cir- 

 cumference. 



3d. The passages situated between the round cellules 

 of the parenchymatous parts receive the sap in larger 

 quantity, considering that their movement is slower. 

 The cellules are thus surrounded by sap, which they can 

 imbibe for the purpose of elaborating. 



We shall see hereafter, that intercellular passages, 

 when dilated, produce the greater part of the Air cavities, 

 and Receptacles of proper juices ; and present thus new 

 support for the life of the vegetable. 



We must not lose sight of the fact, that the cellular 

 tissue is the only elementary organ which exists in the 

 whole vegetable kingdom ; and consequently it is to it, 

 and its modifications, that we must refer all the more 

 general phenomena, the ascent of the sap, and their 

 principal elaboration. 



