﻿292 Evans: The genus Plagiochasma 



The epidermal cells and pores are much the same as in P. crenula- 

 tum, although the number of radiating series of cells around a pore 

 is sometimes as high as eight. The spores are distinctly smaller 

 measuring 50-70 m in diameter (51 m according to Stephani), but 

 they are reticulate in much the same way, and the elaters usually 

 show more or less coalescence of their spiral bands. 



The specimens collected by Hartman in the state of Sonora 

 come particularly close to P. appendiculatum, and their reference 

 to P. crenulatum must be considered provisional. The appendages 

 of the ventral scales are distinctly orbicular in most cases with 

 rounded apices and entire margins, so that they simulate those 

 of the East Indian species very closely. If it were not for the 

 occasional presence of appendages distinctly narrowed toward 

 the apex or even acute it would be quite justifiable to consider 

 the Sonora plant distinct from P. crenulatum. Unfortunately the 

 material is both scanty and sterile, and the appendages are often 

 so thoroughly bleached that their true structure cannot be well 

 made out. It is possible, therefore, that more complete or 

 fertile material would show that the striking peculiarities of the 

 plants were of an accidental character, and for this reason they 

 are included under P. crenulatum. 



Another specimen which requires a few words of comment is 

 the one collected by Munch at San Cristobal. This specimen was 

 distributed by E. Levier in his Bryotheca under a manuscript name 

 of Stephani. The writer finds no sufficient grounds, however, for 

 separating it from P. crenulatum although the appendages of the 

 ventral scales are somewhat smaller and narrower than in typical 

 forms of the species and taper more gradually toward the apex. 

 Combined with this slight difference the epidermal pores exhibit 

 thicker radial walls than is usual and tend to show more than six 

 radiating series of cells around the opening. In other respects the 

 specimen is like P. crenulatum. 



3. Plagiochasma jamaicense (Haynes) comb. nov. 

 Aytonia jamaicensis Haynes, Bull. Torrey Club 34: 58. pi. 6. 



• broadly canaliculate, strap-shaped, 



