148 



Carsten Olsen. 



Anatomy. 



The Leaf. The leaf is dorsiventral as in C. suecica, 

 but differs in having the epidermal cells of about the same size 

 on both surfaces ; also by the cells having strongly thickened 

 outer walls, this latter being caused by the cellulose-mem- 

 brane; the cuticula is quite thin. The palisade-cells are 

 rather thick and short. Apparently there is the same dif- 

 ference between leaf specimens from Greenland and those 

 from more southerly latitudes, as is the case with those of 

 С suecica. The leaves from Greenland are thicker than 

 those from further South, and the extensiveness of the 

 spongy-tissue is much greater in comparison to the palisade- 

 tissue. 



The following table gives a few measurements of leaves 

 from different latitudes: 



On the American specimens the epidermis of both surfaces 

 have strongly undulating sidewalls, while this is much less pro- 

 nounced in those from Greenland (Fig. 11). Stomata are only 

 present on the under surface; the specimens of C. canadensis 



mention diclinous flowers, these must- consequently be very 

 rare, if existing at all. 



