226 American Midland Naturalist Monograph No. 6 



yellow, basally confluent, dorsally cross-striate, bordered, pale and papillose 

 above, trabeculae numerous and closed below, above strongly projecting; inner 

 peristome yellowish, papillose, and with a high basal membrane, segments 

 keeled, split, cilia 2-3, papillose, nodose; spores small; lid shortly and acutely 

 rostrate. 



A genus of about 10 species, occurring on rocks and tree-trunks; 2 species 

 in North America; 1 species in our region. 



1. HoMOMALLiUM ADNATUM (Hedwig) Brotherus 



{Hypnum adnatum Hedwig; Amblystegiella adnata Nichols; 

 Stereodon adnatum Mitten) 



Plate XLIII 



Widely cespitose in thin, closely adherent mats, pale green, or yellowish- 

 green, darker below: stems irregularly branching, creeping, the branches close, 

 short; leaves close, erect-spreading, lanceolate to ovate or oblong, shortly and 

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

 or slightly bistriate at base, the margins often more or less recurved 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 perichaetial broadly 

 ovate, narrowly gradually acuminate, spreading, the inner oblong, erect, more 

 abruptly acuminate, dentate, and costate nearly to the middle: seta erect, 1.5- 

 2 cm long, dextrorse; 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; p>eristome perfect, the teeth promi- 

 nently and numerously trabeculate, hyaline and papillose apically, hyaline- 

 margined and dorsally cross-striolate below, the segments entire and very 

 slightly split, about as long as the teeth, the cilia 1-2, about as long, hyaline 

 and slightly papillose, the basal membrane about two-fifths as high; spores 

 rather incrassate, pale-castaneous, papillose, .009-.012 mm, mature in summer. 



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



West Virginia and Texas. 



Fairly common in our region. Now known from Allegheny, Butler, Fayette, Hun- 

 tingdon, McKean, Washington, and Westmoreland counties. Specimen figured: Lime- 

 stone rocks, Pennsylvania Furnace, Huntingdon Co., July 13, 1909. O.E.J. 



4. Pylaisia Bryologia Europaea 

 ( Pylaisiella Kindberg ) 



Autoicous; slender to rather robust, lustrous, in flat, thin tufts: stem 

 creeping, long, unsymmetrically pinnate; branches short, ascending to erect, 

 often curved, in cross section appearing appressed: leaves homogeneous, more 

 or less imbricate, when moist erect-spreading, often secund, somewhat decur- 

 rent, concave, non-plicate, ovate to lance-oval, more or less long-acuminate, 

 mostly plane and entire; costa double, very short or none; leaf-cells linear- 



