72 



ON THE PLANT-CELL. 



77 



cellular passages, either generally, as in 

 Salvinia (fig. 77.), or in particular spots, 

 as in other plants (fig. 78.). Sometimes 

 they occur in groups, whilst the re- 

 maining epidermis is free from inter- 

 cellular passages, as in Saxifraga sar- 

 mentosa ; and sometimes, in special, ex- 

 cavated pits, surrounded and concealed 



by hairs, as in Nerium Oleander, and species of Bariksia and Dryandra 

 (figs. 79, 80.). This intercellular passage during its growth is entirely 



79 





a 



closed towards the inner part of the leaf by a simple cell. In the course of 

 further development two new cells are formed in this cell, which is 

 subsequently absorbed, and the two new cells gradually assume a semi- 

 lunar form, the concave sides of which, being presented to each other, 

 form an opening between them, through which a communication is 



77 Epidermis of the upper surface of the leaf of Salvinia natans. Here may be 

 seen the simplest form of stomates, as intercellular passages between the epidermal 

 cells. 



!S Epidermis peeled off from an AJlium, with four stomates. 



r9 Transverse section through the leaf of a Banksia. a, a, Epidermis, under which 

 lies, on both sides, a layer of transparent cells, c, Spongy cellular tissue, d, Stretched 

 cellular tissue of the upper half of the leaf; to the right and left, bundles of liber trans- 

 versely cut through, b, A transverse section through one of the little pits of the 

 under part of the leaf, which are clothed with hairs, and at whose base peculiar stomates 

 (e) are found. 



