Jennings: Manual of Mosses — 31. Hypnaceae 253 



but not constricted below the mouth, annulate; peristome normally hypnoid; 

 hd convex, conic-acute. 



A genus of 6 species of forest and meadow in the temperate and cold 

 regions of the Northern Hemisphere; 4 species in North America; 2 species 

 in our region. 



Key to the Species 



A. Cells smooth both sides; stem-leaves not plicate, squarrose-recurved, long and slender- 

 ly acuminate 1. R. squarrosus 



A. Cells dorsally spinose; stem-leaves strongly plicate, spreading, short-acuminate 



2. R. triquetnis 



1. Rhytidiadelphus squarrosus [Linnaeus, Hedwig] Wamstorf 



(Hypnum squarrosum Linnaeus; Hylocomium squctrrosum Bryologia Europaea) 



Widely and softly cespicose, bright green, lustrous: stems robust, but 

 slender, up to 10 or even 15 cm long, procumbent or more or less ascending 

 to erect at the ends, the branchlets rather distant, flexuous, unequal, attenu- 

 ated and more or less sub-flagelliform; stem-leaves crowded, about 3 mm long, 

 abruptly squarrose from a cordate-ovate more or less erect-sheathing base, not 

 secund, imbricated, the squarrose portion long and gradually tapering and 

 channeled, denticulate above, the apical leaves somewhat stellately spreading, 

 branch-leaves smaller but otherwise very similar to stem-leaves; costa short, 

 double, faint; median leaf-cells smooth dorsally, about 8-10:1, narrowly-linear, 

 the alar gradually rectangular-hexagonal, larger, short, opaque to pellucid, 

 numerous, but not forming abruptly differentiated auricles; perichaetial leaves 

 squarrose, the inner linear-acuminate and apically serrate: seta usually 3-4 cm 

 long, flexuous; capsule castaneous, short, ovoid, dorsally gibbous, inclined to 

 horizontal, or even pendent by the cur\'ing of the upper part of the seta; lid 

 convex-conic, rather acute; annulus 2-seriate; peristome normally hypnoid, seg- 

 ments carinately split between the articulations, cilia 3; spores mature in winter 

 or early spring. 



On soil, rocks, or logs, m cool places in moist or wet meadows and borders 

 cf woods in grassy places; Azores, Europe, Asia, and, in North America, 

 from the Arctic regions to the northern United States as far south as Penn- 

 sylvania and Tennessee. 



Rare in our region. Cambria Co.: Lesquereux, at Cresson. (Porter's Flora). Somhr- 

 SEtCo.: Beck Spring, Laurel Ridge. C.M.B. July 26, 1947 (figured). 



2. Rhytidiadelpus triquetrus [Linnaeus, Hedwig] Wamstorf 



(Hypnum triquetrum Linnaeus; Hylocomium tr'iquetrum Bryologia Europaea) 



Plate XLVII 



Very robust, stiff, elastic, bright to yellowish-green, bushy-cespito:-e: stems 

 long, up to 15 or 18 cm, branching unequally and irregularly, sometimes 

 more or less pinnately, reddish, woody, ascending or sometimes erect; stem- 

 leaves large, 4-5 mm long, stiff, scarious, divaricately or horizontally spreading 

 both wet and dry, widely cordate- to deltoid-triangular, widely rounded- 



