﻿Evans: The genus Plagiochasma 293 



times with adventive branches, sometimes innovating at the apex, 

 rarely (if ever) dichotomous, margins crenulate, more or less 

 crispate, mostly about i cm. long and 5-7 mm. wide, thickness of 

 thallus about one eighth the width; epidermis composed of thin- 

 walled cells with small but distinct trigones and a smooth cuticle, 

 the cells about 30 /z in diameter ; pores slightly elevated, rather large, 

 surrounded by about eight (five to ten) radiating series of cells 

 with two to four cells in each series, radial walls slightly thickened ; 

 aeriferous layer about three-fourths the thickness of the thallus 

 in the median region, fairly compact, with the air-spaces a littla 

 wider than the green cells; ventral scales lunulate to ovate, purple, 

 slightly overlapping, irregularly sinuate along the margin with 

 vestiges of slime papillae, cells containing oil-bodies very few 

 and scattered, the scales abruptly contracted into one or (rarely) 

 two ovate appendages, constricted and plicate at the base, entire 

 or vaguely and irregularly dentate or crenate along the margin, 

 often showing vestiges of slime papillae, gradually narrowed 

 toward the apex into an apiculum usually two to three cells long; 

 inflorescence monoicous: cf inflorescence (in the few observed 

 cases) near the apex of a thallus, the 9 receptacles being borne 

 (usually in a series) on the following joint or apical innovation; 

 peduncle of carpocephalum 1-1.5 cm. long; carpocephalum mostly 

 plano-concave at the apex and bluntly two- to four-lobed, usually 

 maturing two sporophytes; scales of carpocephalum lanceolate 

 to linear-lanceolate, acuminate, entire or sparingly and irregularly 

 dentate: spores 70-85 /j, in diameter, yellowish brown, minutely 

 verruculose, reticulate but with the meshes often indistinct, 

 spherical face with about twelve meshes (eight or nine marginal), 

 plane faces with about four meshes; elaters gradually attenuate, 

 mostly 250-375 M long and 8 /x in maximum diameter, with two 

 or three spirals, sometimes slightly coalescent. 



The following specimens have been examined : 



Jamaica: Chestervale, Blue Mountains, altitude 900 m., 

 February, 1903, L. M. Underwood 1173 (type), 1177 (both mixed 

 with Reboidia hemisphaerica [L.] Raddi). 



No other localities for the species are known. 



The above description is largely compiled from the original 

 paper of Miss Haynes, only a few details having been added. The 

 specimens studied bear a very strong resemblance to the Reboidia 

 with which they are growing, the size, general habit, and pigmented 

 margin being almost exactly the same. The color, however, is a trifle 

 redder in the Plagiochasma and of course the dorsal position of the 

 carpocephala will at once separate it from the Reboidia, where the 



