(I2 9 ) 



Plagiobryum argenteoides R. S. Williams sp. now 



With the appearance of Bryum argenteum. In den 



tufts up to i cm. high. Stems simple or branching, vineous 

 red, radiculose below, in cross section showing an outer wall 

 of one layer of irregular, somewhat thick-walled cells, with 

 ground tissue of very large, thin-walled cells, becoming 

 smaller toward center and enclosing a distinct central strand. 

 Leaves concave, appressed, broadly ovate, with short abrupt 

 point, entire, mostly \ mm. long or less or occasionallv the 

 terminal leaves lanceolate pointed and up to i mm. long. 

 Costa vanishing from \ to -| up. Upper \ of leaf usually 

 hyaline. Alar cells and most basal cells square (sides 12 to 

 16 mm.) to short rectangular (1 to 2). Median cells irregu- 

 larly rhomboidal to oblong-linear, up to .040 or .050 mm. by 

 .012 mm. Cell walls somewhat thickened, especially above. 

 (Plate 21.) 



This species is distinguished from the preceding by its 

 small size and nerve vanishing far below the apex as well as 

 by the short, square alar cells. Found on bare rock in dry 

 places on the Yukon River, just below Dawson, March 19, 

 1899 (659). 



Karl Mueller described in Flora, 70: 221, 1887, a Bryum 

 bidlatum, which he compares with small Plagiobryum Zierii. 

 As this comparison well fits my plant I was in some doubt as 

 to the two being distinct, but having lately received a speci- 

 men of bidlatum from the Mueller collection, through the 

 kindness of the Berlin authorities, the two plants prove to be 

 perfectly distinct, bidlatum being an Anomobryum {Sclcro- 

 dictyon) as described. 



Mnium medium B. & S. Left bank of the Klondike River 

 just below Bonanza Creek, not common, also collected at 

 Skagway, growing abundantly under the heavy evergreen 

 forests. Cell walls thickened and pitted, cells somewhat 

 elongated, not in oblique rows, stomata immersed (661). 



Mnium rugicum Laur. Head of Lake Bennett. In 

 these specimens the leaf-cells are somewhat obliquely elon- 

 gated but not in rows. The leaves are narrow at base, not 

 decurrent and without distinct rectangular basal cells, the 

 margin with very small irregular teeth or entire (662). 



