276 A MANUAL OF MOSSES 



2-4(-6) :1, alar cells more or less plainly diif erentiated ; costa 

 complete or sub-percurrent : seta elongate, castaneous ; capsule 

 inclined to horizontal, early symmetric or somewhat dorsally 

 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-subu- 

 late, broadly bordered, dorsally cross-striate, apically pale and 

 papillose, the margin step-like, the trabeculae strongly project- 

 ing; inner peristome yellow, finely papillose, with high basal 

 membrane, segments piostly carinately split, cilia complete, 

 nodose to short-appendiculate ; lid high-convex and apiculate 

 or acute ; spores small. 



A genus of about 13 species, in damp places or in water, 

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

 America ; at least 3 species occurring in our region. 



Key to the Species. 



a. Leaves non-dgcurrent, entire or indistinctly and remotely serrate. 



b. 

 a. Leaves mostly decurrent, mostly with small but distinct teeth. 



c. 

 b. Leaves rather obtuse. 1. H. fluviatile. 



b. Leaves more or less sharply acute. 2. H. tenax. 

 c. Costa sub-percurrent to percurrent. 3. H. Alicinum. 



c. Costa excurrent. d. 



d. Leaves decurrent, auriculate, basally excavate. 



(H. fallax ■ (Bride!) 

 Brotherus). 

 d. Leaves non-decurrent, non-auriculate, not basally excavate. 



(//. notcrophilum (Sulli- 

 vant) Wamstorf). 



1. Hygroamblystegium fluviatile | Swartz] Loeske. 



(Amblystegium fluviatile Bryologia Europxa; Hypnum fluviatile 



Swartz). 



(Plate XXXIX) 



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 scarce- 

 ly pinnate; leaves oblong-lanceolate to oblong-ovate, not 

 markedly narrowed below, rather remote, erect-spreading, es- 

 pecially wheii 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, hexa- 

 gonal-rhomboid, about 3-6:1, the basal cells rectangular, pel- 

 lucid, sometimes, somewhat opaque, strongly incrassate, not 

 forming auricles' sometimes quite orange; perichastial 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 



