152 



HETEROPHYLLY 



[CH. 



B 



FIG. 99. Polygonum amphibium, L. A , branch of aquatic plant with floating leaves. 

 B, branch of xerophilous plant inhabiting littoral dunes. [Massart, J. (1910).] 



FIG. 100. Polygonum amphibium, L. A, upper epidermis, and B, lower epidermis of 

 floating leaf, cf. Fig. 99^. C, upper epidermis, and D, lower epidermis of xero- 

 philous leaf, cf. Fig. 99 B. The elements marked with a cross are reservoir cells. 



[Massart, J. (1910).] 



