OF WESTERN PENNSYLVANIA 275 



slenderly acuminate, entire or nearly so, concave, ecostate or 

 slightly bi-striate at base, the margins often more or less re*» 

 curved below, the leaves 0.6-1.0 mm. long; median leaf-cells 

 somewhat pellucid, sub-rhomboidal, prosenchymatous, about 

 4-8 :1, the apical often shorter, the alar numerous, smaller, more 

 incrassate and opaque, quadrate and extending along the 

 margin to one-fourth or one-third the length of the leaf; outer 

 perichsetial broadly ovate, narrowly gradually acuminate, spread- 

 ing, the inner oblong, erect, more abruptly acuminate, dentate, and 

 costate nearly to the middle: seta erect, 1.5-2 cm. long, dex- 

 trorse; capsule arcuate, oblong, narrowed to a distinct neck, 

 cernuous, reddish or yellowish, when dry constricted below 

 the mouth but not wrinkled; lid paler, acutely conic; annulus 

 present; exothecial cells rounded-hexagonal near the rim, 

 rectangular below; peristome perfect, the teeth prominently 

 and numerously trabeculate, hyaline and papillose apically, 

 hyaline-margined and dorsally cross-striolate below, the seg- 

 ments entire and very slightly split, about as long as the teeth, 

 the cilia about as long, hyaline and slightly papillose, the 

 basal membrane about two-fifths as high; spores rather in- 

 crassate, pale-castaneous, papillose, .009-.012 mm., mature in 

 summer. 



On rocks and on bases of trees in woods ; Asia and from 

 lower Canada to North Carolina and Texas. Fairl}' common 

 in our region. 



Allegheny : Schenley Park, Pittsburgh, August 20, 1905, 



and on base of Acer saccharnm, Guyasuta 

 Hollow, November 8, 1908. O. E. J. 

 Fayette : Ohio Pyle, May 30-31, 1908. O. E. J. and 



G.K.J. 

 Huntingdon : On limestone rocks, Pennsylvania Fur- 

 nace, July 13, 1909. O. E. J. (Figured). 

 McKean : On base of tree, Hawkins' Hollow, Brad- 



ford, October 18, 1895. D. A. B. 

 Westmoreland : On soil in woods. Hillside. May 22, 1909. 

 O. E. J. 



4. HYGROAMBLYSTBGIVM Loeske. 



Autoicous or dioicous : slender to quite robust, mostly 

 stiffly cespitose, dark-green to blackish-green, dull : stem more 

 or less elongate, mostly floating, rarely more or less erect, most- 

 ly rather regularly pinnate, with forward-directed, rarely erect, 

 mostly simple branches; leaves close, spreading to secund, 

 concave, non-plicate, not at all or but slightly decurrent, rarely 

 long-decurrent, mostly ovate to oblong-lanceolate, long- 

 acuminate, margins plane, entire or remotely indistinctly 

 denticulate; costa strong, short or percurrent, sometimes 

 thickly excurrent; cells green, prosenchymatous, hexagonal, 



