CLAWSON: ANATOMY OF JANUSIA. 197 



isade cells are only found in the upper surface, except over the 

 mid rib, where large cells resembling the border parenchyma 

 are found (figs. 24 and 33). In most of these there is an 

 abundance of tannin, while others seem to be used as water- 

 storage cells. 



The spongy parenchyma is similiar to that found in the 

 usual leaf. The lower epidermis has cells somewhat smaller 

 than the upper epidermis, and in it are found both stomata 

 and pores (fig. 2.5). The number of free endings of the veins 

 is about 100 per square mm., having an average distance be- 

 tween them of .011 mm. The veins in the mesh work average 

 in distance apart from .2 mm. to .9 mm. Having the endings 

 so close together would seem to indicate that a great deal of 

 water might pass through them. So far as this anatomical 

 detail is concerned, the leaf is equipped to supply rapid tran- 

 spiration of water. 



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