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Evans: The genus Plagiochasma 



being often composed of only two cells. In this respect it ot 

 course recedes most widely from P. jamaicense. The cells forming 

 the pore show in a marked degree the peculiarity described by 

 Leitgeb in the case of P. crenulatum. They appear as if shoved 

 under one another, and this condition is often so marked that the 



second and third cells in each radiating series lie almost directly 

 under the cell next the opening. The cells in each series are 

 separated by very thin walls, and the lines of junction between 

 these walls and the cuticle are more or less convex when seen from 

 above, thus giving the pore a somewhat distinctive, flower-like 

 appearance. 



The ventral scales resemble those of P. nipestre, although the 

 basal portion shows a very narrow border of contorted cells and 



