LECT. X.J ANATOMY OF LEAVES. 591 



589), taken from the leaf of Iris Germanica, 

 we perceive that not only the cut edges (c.) of 

 the cells appear double; but that where some 

 of the cells deviate from the hexagonal figure, 

 there are evident interstitial spaces (a. d.) be- 

 tween them, which if the cells were not distinct- 

 vesicles would not occur. These interstices have 

 been noticed by Leuwenhoek, Treviranus, Com- 

 paretti, and M. Kieser; the last of whom sup- 

 poses them to exist at every angle of every cell, 

 and by their conjunction to form canals which 

 surround it ; and to be the only passages by which 

 the fluids are conveyed through the cellular sub- 

 stance*. It is unnecessary to point out the im- 

 probability of this opinion ; and it is sufficient foi 

 our purpose to demonstrate the existence of these 

 interstices, to prove the double nature of the in- 

 tercellular partitions. This is very evident in the 

 elongated cells, which we have seen exist near 

 the upper disk of many leaves ; and in the spaces 

 formed by the conjunction of these only, have I 

 been able to perceive any resemblance to the in- 

 tercellular canals of M. Kieser. 



A question arises in consequence of the sup- 

 position that each vesicle is a distinct sac: in 

 what manner do the cells communicate with each 

 other, and with the vessels which they surround ? 



* Mem. sur I* Organisation des Plantes, p. 20. 



