Jennings: Manual of Mosses — 31. Hypnaceae 231 



A genus of about 10 species, in very damp or frequently submerged places 

 or in water, mostly in temperate or cooler regions; 5 species occur in North 

 America; at least 5 species in our region. 



Key to the Species 



A. Leaves non-decurrent, entire or indistinctly and remotely serrate B 



A. Leaves mostly decurrent, mostly with small but distinct teeth C 



B. Stem-leaves lance-oblong to oblong-ovate with rather obtuse point 1. H. fluviatile 



B. Stem-leaves triangular lanceolate to triangular ovate, sub-obtuse to acuminate D 



C. Costa sub-percurrent to percurrent; leaves with decurrent auricles of inflated cells 



4. H. filicimim 



c:. Costa excurrent; leaves non-decurrent, non-auriculate, not basally excavate 



3. H. Jioterophilum 



D. Stem-leaves more or less acuminate 2. H. irriguum {^ tenax) 



D. Srem-leaves sub-obtuse to acute 3. H. orthocladon 



1. Hygroamblystegium fluviatile [Swartz] Loeske 



(Amblystegium fluviatile Bryologia Europaea; Hypnum fluviatile Swartz) 



Plate XLIII 



Robust, aquatic, floating in flat and elongated tufts, soft, olive- to dark- 

 green, devoid of leaves below: stems with few branchlets, long, the branchlets 

 more or less parallel and scarcely pinnate; leaves oblong-lanceolate to oblong- 

 ovate, not markedly narrowed below, rather remote, erect-spreading, especially 

 when dry, non-decurrent, gradually tapering to a short, blunt point, entire or 

 very faintly serrulate, very concave, the margins more or less recurved at base; 

 costa thick and strong, yellowish, ending in the apex; median leaf-cells loose, 

 he.xagonal-rhomboid, about 3-6:1, the basal cells rectangular, pellucid, some- 

 times somewhat opaque, strongly incrassate, not forming auricles, sometimes 

 quite orange; perichaetial leaves erect, strongly costate: seta about 1.5 cm long, 

 castaneous, dextrorse; capsules about 2.5 mm long, oblong-cylindric, sub-erect, 

 sub-arcuate, rather thick-walled, yellowish-brown, when dry and empty strongly 

 arcuate and constricted below the mouth; below the 2-3-seriate annulus ihe 

 exothecial cells small and rounded-quadrate; peristome slightly irserted, teeth 

 strongly confluent at base, dorsally cross-striolate, brownish below, apically 

 hyaline and papillose; segments about as long as teeth, carinately spht, the 

 three nodose cilia about as long, the basal membrane about two-fifths to one- 

 half as high as teeth; spores medium-walled, minutely papillose, brownish, 

 about .016-.019 mm, mature in early summer. 



On earth and on rocks and stones in running water, usually m non-cal- 

 careous districts; Europe, and, in North America, from Newfoundland to 

 New Jersey and westward to the Mississippi. Most of our specimens seem to 

 belong to forma brevijoliuvi Boulay, with concave, oblong-ovate leaves, sub- 

 obtuse at apex, and with colored opaque basal cells. 



Now known from Allegheny, Beaver, Butler, Cameron, Fayette, McKean, and West- 

 moreland counties, all in the non-glaciated area. Specimen figured: Shades Ravine, Black- 

 burn, Allegheny Co.. June H, 1908. O.E.J. 



