FORM OF THE PLANT- CELL. 



8) 



73 



formed with the intercellular passage in the parenchyma. These semi- 

 lunar cells are not found in Salvinia, nor in Marchantiacece*, but are 

 found doubled and trebled in some Proteacece.\ 



In the arrangement of the parts of these organs many varieties are 

 found, especially in the relation of the stomatic cells with the intercellular 

 passage, and the arrangement of the epidermal cells forming the inter- 



cellular passage ; these peculiarities distinguish families and genera, as 

 in the Cactacece, the Grasses, Aloe, Tradescantia, &c. The stomatic 

 cells may be pushed somewhat outwards with their edges above the 

 epidermal cells, or they may lie upon the same plane (fig. 81.), or they 

 may lie entirely under the edge of the cells of the epidermis (fig. 82.). 

 With regard to the second form here mentioned, we frequently see the 

 cells lying next to the intercellular passage coloured differently, and 



* In these plants the intercellular space ordinarily found under the stomates is beset 

 with peculiar flask-shaped papillary cells. 



f See Mohl, Ueber die Spaltoffhungen der Proteacese, in N. A. A. L. C. N. C. 

 t. xvi. p. 2. 



80 A parallel section of the under surface of the leaf of a Banksia, from which 

 the epidermis is removed, x, The vascular bundles forming the network of the leaf. 

 a, b b, Three little pits, which vary in appearance according as the section by which the 

 epidermis was removed, cut deeply or superficially. The lower b, A pit with the hairs 

 and stomates at the base : a exhibits the base of the pit, with the stomates ; b exhibits 

 the same, but the spongy cellular tissue is seen below, o, The epidermis clothing the 

 base of the pit is removed, leaving nothing but the spongy cellular tissue. 



81 Perpendicular section through the epidermal tissue of the leaf of a Stock, c, The 

 epidermal cells covered with a layer of secretion (6), which, at the most external parts, is 

 formed out of a more compact layer, a, Entrance to the stomate through the secreted 

 layer. 



