OF WESTERN PENNSYLVANIA 297 



2. Rhytidiadelphus triquetrus [Linnaeus] Warnstorf. 



(Hypmtiii triquetrwn Linnaeus; Hylocomium triquetruin Bryo- 



logia Europjea). 



(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; perichjetial 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. 

 Not uncommon in our region. 



Cambria : T. C. Porter. (Porter's Catalogue). 



Elk : McMinn. (Porter's Catalogue). 



McKean : 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. RHYTIDIUM (Sullivant) Kindberg. 

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

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



