﻿Evans: The genus Plagiochasma 279 



Thallus pale green and glaucous above with a narrow purple 

 border, plane or somewhat canaliculate, strap-shaped, sometimes 

 forking, sometimes innovating at the apex or with ventral branches, 

 margin undulate, scarcely or not at all crispate, mostly 1-2 cm, 

 long, and 5-7 mm. wide, thickness of thallus about one tenth the 

 width ; epidermis composed of thin-walled cells with small trigones 

 and a thin minutely roughened cuticle with a waxy deposit, the cells 

 mostly 18-30 n in diameter; pores not elevated, small, surrounded 

 by four to six cells in a single series or in an incomplete double 

 series, radial walls usually distinctly thickened; aeriferous layer 

 about one half the thickness of the thallus in the median portion, 

 fairly compact with the air-spaces a little wider than the green 

 cells, tending to extend at right angles to the epidermis; ventral 

 scales deep purple, obliquely lunate to ovate, entire, with a few 

 scattered cells containing oil-bodies, gradually narrowed into one 

 or two (very rarely three) ovate-lanceolate to lanceolate or subu- 

 late appendages, acute to acuminate at the apex, slightly or not 

 at all constricted at the base, entire: inflorescence monoicous: 

 cf inflorescence on a small ventral branch or on an ordinary 

 branch: 9 receptacles borne singly or in a median longitudinal 

 series; peduncle short, mostly 3 mm. long or less; carpocephalum 

 concave at the apex, with two or three apiculate lobes, maturing 

 two or three sporophytes; scales of carpocephalum abundant, 

 narrowly subulate with elongated filiform points, entire: spores 

 yellowish brown, 70-90 /j, in diameter, minutely rugulose, reticu- 

 late, spherical face mostly with twelve to fifteen meshes, plane 

 faces usually with three or four meshes, the meshes on both 

 spherical and plane faces often incomplete; elaters mostly 250- 

 400 /x in length and about 10 ji in diameter, with two to four spirals, 

 sometimes more or less coalescent. [Figs. 1-4.] 



The following specimens have been examined : 



New Mexico: Organ Mountains, Filmore County, altitude 

 1800 m., July, 1897, E. 0. Wooton. 



Arizona: without definite locality or date, H. H. Rushy; Santa 

 Catalina Mountains, April, 1913, W.A. Ca«»o»; Soldier's Canyon, 

 Santa Catalina Mountains, September, 1913, G. E. Nichols. 



Bata California: without definite locality or date, T. S. 

 Brandegee 25. 



DuRANGO: Tejamen, August, 1906, E. Palmer 473, 474; city 

 of Durango and vicinity, 1896, E. Palmer 709 (mixed with Tar- 

 gionia hypophylla L.). 



Jalisco : wet banks and rocks. Barranca de Oblatos, Guadala- 

 jara, September, 1908, Barnes & Land 122, 123, 134. 



