24 



ELEMENTARY ORGANS OP PLANTS. 



or slit except accidentally ; and these apparent pores and slits 

 are, in reality, pits and chinks left by the non-deposition of 

 sedimentary matter at that particular part of the cell-wall, 

 and consequently visible by the greater amount of trans- 

 parency there. 



19. The chinks and pits in contiguous cells usually corre- 

 spond, and hence one reason for this peculiar deposition of 

 the sclerogen is very obvious. By it the lateral communica- 

 tions between the several cells composing the tissue are kept 

 open, notwithstanding this thickening of their walls, the sap 

 permeating through the vegetable tissues at these particular 

 parts. These lateral passages and their nature are clearly 

 shown in Fig. 4, which is a transverse and longitudinal 



Fig. 4. 



section of a portion of four cells of the woody tissue of Pla- 

 tanus ocoidentalis, or the Buttonwood, "highly magnified, 

 showing the canals or deep pits in the thickened walls, and 

 their apposition in adjoining cells; on the cross-section the 

 layers of deposit are more plainly visible."''' 



* Gray's Botanical Text-Book. 



