40 



ORGANOGRAPHY. 



Fig. 80. 



Fig. 81. 





c-^f-s^^-^ 







Fig. 80. Section through the leaf of a Banksia. a, a. Epidermis with two 

 rows of cells, c. Spongiform parenchyma. 6. Hairs which are contained 

 in little depressions on the under surface of the leaf. After Schleiden. 



Fig.Sl. Section through the leaf of Oleander, showing the epidermis com- 

 posed of three layers of thick-sided cells, and placed above a compact 

 parenchyma of vertical cells. After Brongniart. 



belongs the merit of first establishing this point, has proposed 

 the name of cuticular layers of the epidermis (fig. 82, 6), for these 

 secondary deposits in the epidermal cells. 



Fig. 82. 



Fig. 83. 



Fig. 82. The epidermis of Iloya camosa treated with caustic alkali, a. 

 The cuticle separating : 6. the swollen, laminated, cuticular layers of the 



epidermal cells. After Mohl Fig. 83. Tliickened epidermal cells of a 



Cactus. After Schleiden. 



The cells of the epidermis are always filled with colourless 

 fluids ; the green or other colours wliich leaves and otlier organs 

 assume is due tlierefore to colouring matters of various kinds 

 which arc situated in the subjacent parenchymatous cells, and 

 which sliow through the transparent epidermis. In tlie epider- 

 mal cells of many plants, waxy matter is contained; in those 

 of Chara, carbonate of lime ; and in those of Equiseta, and the 

 Grasses, silica is met with in such abundance, tliat, if the organic 

 matter be removed by the agency of heat or acids, a perfect 

 skeleton of the structure will be obtained. These substances arc 

 probably deposited in the walls of the cells. 



