﻿EvAxs: The genus Plagiochasma 303 



and the vcMitral scales afford differential characters of importance. 

 The pores are much like those of P. jamaicense and tend, if any- 

 thing, to be even more complex, frequently showing nine radiating 

 series of cells around the opening with four cells in each series. 

 The radial walls separating the series are, moreover, strongly 

 thickened. The ventral scales bear considerable resemblance to 

 those of P. Landii and P. Wrightii. The basal portion shows a 

 vague border of contorted cells, the margin itself being indistinctly 



sinuous or crenulate with vestiges of slime papillae. The appen- 

 dages, usually borne in pairs, are lanceolate to ovate and commonly 

 acute. According to Stephani they are strongly constricted at 

 the base, but this condition is apparent rather than actual and 

 seems to be due to the presence of basal folds. When these are 

 not present the appendages show no appearance of constriction. 



