148 



ORGANOGRAPHY. 



Fig. 285. 



ordinary leaves it is moderately de- 

 veloped, and they are then thin and 

 flattened ; while in others it is formed 

 in large quantities, when they be- 

 come thick and fleshy, and are 

 termed succulertt. 



The parenchyma also varies in 

 its form and arrangement ; in or- 

 dinary flat leaves we can readily 

 distinguish two distinct layers cf 

 cells, one of which is placed be- 

 neath the epidermis of their upper 

 surface, and the other bei-eath that 

 of the lower. The whole of the 

 cells are commonly green from the 

 presence of chloropliyll in their in- 

 terior. Beneath the epidermis of 

 the upper surface we find one {fig. 

 285), two, or three layers of oblong 

 blunt cells {fig. 286, ps), placed 

 perpendicularly to the surface of the leaf. These cells are also 

 placed closely against each other, and have no intervals but 

 those formed by the unequal contact of such cells, except 

 where stomata occur st, when spaces may be observed m, by 



Fig. 286, 



Fig. 28.5. Vertical section of a 

 leaf of the White Lily highly 

 magnified, showing tlie epider- 

 mis of both the upper and lower 

 surfaces, with the intervening 

 parenchyma. 



Z-Vj/. 286. Vertical section of a leaf of the Melon, highly magnified, es. Epider- 

 mal tis.Mie of the upper surface, furnished with hairs,;*, and stomata, st. 

 ex. Epidermal tissue of the lower surlace. pn. Three layers of upper i)aren- 

 chvmatous cells. ;<('. Parenchymatous ceils near to the epidermal tissue 

 of the lower surface, fv. Fibro-vascular bundles, vi. Cavities connected 

 with the stomata. /. Cavities between the loose spoi-giform pareuchyma. 



