230 American Midland Naturalist Monograph No. 6 



cave, subscarious, lustrous, ovate to long-lanceolate, about 0.7-0.9 mm long, 

 acuminate, the margin entire and recurved below; leaf-cells all medium-walled, 

 at apex rhomboidal, the median linear-rhomboidal prosenchymatous, about 

 6-9:1, the alar distinct, quadrate and relatively large, extending up the mar- 

 gin; inner perichaetial leaves about twice as long as the branch-leaves, ecostate, 

 more acuminate: seta erect, 10-15 mm long, smooth, lustrous, dark-castaneous, 

 sinistrorse; urn of capsule about! 1:0-2.5 mm long, erect, symmetric, oblong- 

 cylindric, castaneous, not narrowed below the mouth when dry; op>erculum 

 about two-fifths the length of the urn, slenderly and obliquely but bluntly 

 rostrate; annulus persistent, large, 2-3-seriate, and appearing like modified 

 upper exothecial cells; peristome -teeth rather deeply inserted, linear-lanceolate, 

 light yellowish-brown, strongly about 15-18 trabeculate, widely hyaline-bor- 

 dered, papillose below in irregular and often radiating lines, but not cross- 

 striate below as in most hypnaceous peristomes, lamellae and divisural line 

 rather indistinct; segments about two-thirds as long as teeth, linear, narrow, 

 arising from a very low basal membrane, more or less carinately cleft; cilia 

 none; exothecial cells quadrate to irregular or oblong-hexagonal, yellowish; 

 spores about .014-. 018 mm, yellowish, minutely roughened, medium-walled, 

 mature in autumn; gemmae often abundant in the axils of the upper leaves. 



On bark at base of trees, on decaying logs, stumps, and in woods; widely 

 distributed in the Northern Hemisphere; in North America from New Bruns- 

 wick to the Pacific and south to the Gulf of Mexico. 



Very common in our region at lower altitudes, rarely found in the mountains or 

 plateau uplands. Known from the following counties: Allegheny (more than 50 collec- 

 tions), Armstrong, Beaver, Butler, Crawford, Erie, Fayette, Greene, Somerset, Washing- 

 ton, and Westmoreland. Sf>ecimens figured: On rotten log, oak woods, Keown, Alle- 

 gheny Co., Nov. 14, 1909. O.E.J. 



6. Hygroamblystegium Loeske 



Autoicous or dioicous: aquatic or sub-aquatic; 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, mostly 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-acu- 

 minate, margins plane, entire or remotely indistinctly denticulate; costa strong, 

 short or percurrent, sometimes thickly excurrent; cells green, prosenchymatous, 

 hexagonal, 2-4(-6) :1, alar cells more or less plainly differentiated; perichaetial 

 leaves elongate-lanceolate, costa complete or sub-percurrent: seta elongate, 

 castaneous; capsule inclined to horizontal, early symmetric or somewhat dor- 

 sally gibbous, oblong-cylindric, later more or less arcuate, when dry and empty 

 constricted below the mouth; peristome-teeth dark-yellow to orange, more or 

 less basally confluent, lance-subulate, broadly bordered, dorsally cross-striate, 

 apically pale and papillose, the margin step-like, the trabeculae strongly pro- 

 jecting; inner peristome yellow, finely papillose, with high basal membrane, 

 segments mostly carinately split, cilia complete, nodose to short-appendiculate; 

 lid high-convex and apiculate or acute; spores small. 



