592 



CONSERVATIVE ORGANS. 



[LECT. x. 



Malpighi, aware of the necessity of an explanation 

 of this point, maintains that a small tubular pro- 

 duction (a. a. 37.) issues from each cell or vesicle, 

 by which it communicates with the contiguous 

 cells (b. b.), and with the vascular system of the 

 leaf (c. c.); and has given a microscopic repre- 

 sentation of this cellular structure in the Cactus 

 (37.) to illustrate his position. A similar idea 

 was entertained, also, by M. de Saussure, who 

 describes the cellular part of the leaf as a con- 

 geries of minute transparent vessels, which are so 

 dilated between their junctions as to assume the 

 appearance of cells or vesicles. But, notwith- 

 standing the high authority advancing this opi- 

 nion, my observations prevent me from according 

 with it: since in no leaf, which I have examined, 

 have I been able to detect these communications. 

 In the Cactus, if we select a small portion of a 

 vessel with some cellular matter adhering to it, as 

 in the minute morsel (38.), under the microscope, 

 before us, we perceive that the cells (b. b. b.) are 



