OF WESTERN PENNSYLVANIA 297 



2. Rhytidiadelphus triquetrus [Linnaeus] \\~arnstorf. 



(Hypniun triquetrum Linnaeus: Hylocomium triquetrum Bryo- 

 logia Europaea). 



(Plate XLIII) 



Robust, stiff, bright to yellowish-green, bushy-cespitose : 



stems long, up to 15 or 18 cm., branching unequally and ir- 

 regularly, 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- 

 auriculate at base, the insertion narrow and decurrent ; leaves 

 plicate, denticulate, papillose dorsally, gradually tapering 

 above to a sub-acute apex; branch-leaves narrower and smaller 

 towards the ends of the attenuate branches; costa forked, or 

 of two parallel divisions reaching about three-fourths the 

 length of the leaf; perich?etial leaves non-costate, the acumina- 

 tions squarrose ; median leaf-cells linear, about 8-10:1, at the 

 angles oblong-hexagonal, pellucid, not usually forming distinct 

 auricles, the upper cells dorsally forming spinulose papillae: 

 seta 1.5-2.5 cm. long, rather rigid, lustrous, castaneous ; capsule 

 turgid-oblong, large, castaneous, about 3 mm. long, dorsally 

 gibbous, inclined or more nearly horizontal by a curve in the 

 upper part of the seta, when dry more or less plicate and con- 

 stricted below the mouth ; the exothecial cells rounded-hexa- 

 gonal, rather small, incrassate, castaneous: lid conic, acute; 

 peristome normally hypnoid, the teeth orange-yellow, strongly 

 trabeculate, dorsally lamellate, the lamellae papillose but non- 

 striate, projecting to form a distinct border; the segments 

 carinately split, the cilia 2 (or 3) and about as long as the 

 segments, stout, the basal membrane reaching about one-half 

 the height of the peristome: spores medium-walled, smooth, 

 yellowish, .018-.025 mm. 



On shaded banks in woods with a moderate amount of 

 moisture, or in swamps ; Europe, Asia, northern Africa, and, in 

 North America from the Arctic regions south to the northern 

 United States, and along the mountains in North Carolina. 

 Xot uncommon in our region. 



Cambria 



Elk 

 McKean 



T. C. Porter. (Porter's Cataloue). 



Me Minn. (Porter's Cataloue). 



On decaying leaves under hemlocks, 

 Marilla Brook, Bradford, June 5, 1895 

 (Figured), and September 29, 1894; Ben- 

 nett Brook, July 15, 1893. D. A. B. 

 Washington : Linn and Simonton. ( Porter's Catalogue). 



13. RHVTIDfUM (Sullivant) Kindberg. 



Dioicous : very robust, in wide, loose, yellowish or brown- 

 ish-yellow tufts : when dry stiff and lustrous : stems long, tumid. 



