391 



ched. The epidermal cells have undulating radial walls. The 

 stomata are more numerous upon the upper surface, but the 

 number varies somewhat in the different leaves. In the speci- 

 mens irom Denmark I found from 57 to 83 per sq. mm. upon 

 the upper surface, and about 50 per sq. mm. upon the lower, 

 and the specimens from Greenland have about the same number. 



Fig. 35. R. reptans. 



A, Fragment of transverse section of leaf of land-form (Denmark; ""i). B. Transverse 

 section of leaf of submerged form (Denmark; ""/i). C, Epidermis of the upper surface of 

 leaf of land-form (Denmark; ^^/i). D, Epidermis of the lower surface of leaf of land-form 

 (Denmark ; "^/i). È, S\irface section of palisade-cells of land-form (Denmark ; "''/i), F. 

 Surface section of spongy parenchyma of land-form (Denmark; w/j). 0, Longitudinal 

 section through the leaf-apex oj land-form (Denmark; -"/i). 



In the Danish specimens there is also some chlorophyll in the 

 epidermis; (Fig. 35, C, D). A few thick-walled hairs of the 

 usual type occur. The bundles are without stereom. The radial 

 leaf is rounded and has an axile bundle. The mesophyll and 

 the epidermis consist of elongated cylindrical cells; stomata 

 are present, but in no great number. This leaf resembles that 

 of Batrachinm, but has larger intercellular spaces. Fig. 35, B 



