THE LEAF 



neighbourhood of the stomata. Lastly, part of the vascular network 

 is shown dimly in a still lower plane. The strands lie between the 

 palisade and the spongy paren- 

 chyma, and the conducting 

 system is thus in near relation 

 to the bases of the oblong pali- 

 sade cells. 



In the Dicotyledons the 

 stomata are relatively small, 

 and irregular in their orienta- 

 tion. They are shown in section 

 in Figs. 44, 45, and in surface 

 view in Fig. 46. In Monocotyle- 

 dons they are usually larger, 

 and their orientation regular. 

 The large stoma of Narcissus 

 serves as an example (Fig. 47). 

 Its guard-cells have a charac- 

 teristic outline, each with a 

 projecting ridge on its oblique outer and inner walls. The stoma 

 is here slightly sunk below the outer surface of the leaf. The 



FIG. 47. 



Drawings from the same Stoma of Narcissus, in 

 surface view. A, in the open ; B, in the closed state. 

 F. O. B. (X250.) 



Fie. 48. 



Stoma of Narcissus in transverse section, showing its relation to the adjoining 

 epidermal cells and to the mesophyll below. Two of the cells of this tissue are 

 drawn in in- detail, that to the right as seen in surface view from without ; that to 

 the left in optical section. The chloroplasts are black. ( x 300.) F. O. B. 



level of the stoma relatively to the leaf-surface varies in different 

 types according to their habitat. In plants of temperate climates 



K. R. E 



