OF WESTERN PENNSYLVANIA 97 



Strand, thickly foliate, radiculose, the branches reaching to 

 about the same height ; leaves more or less keeled, erect- 

 spreading, mostly lanceolate from a broad base, the margin 

 revolute ; costa well developed, upwards cylindrical, rarely ex- 

 current ; leaf-cells small, rounded-quadrangular, often smooth, 

 sometimes the basal elongate and pellucid : seta long, erect ; 

 capsule erect, oblong to cylindric, sometimes slightly arcuate, 

 short-necked, smooth ; no annulus ; peristome inserted on the 

 edge of the urn, papillose, the trabeculae projecting; teeth 16, 

 plane, narrow, undivided, or perforate, or cleft to the base into 

 filiform parts approximate in pairs ; spores small ; operculum 

 conic-rostrate ; calyptra cucullate, smooth. 



A widely distributed genus of 80 species, on soil or rock, 

 mainly in temperate regions; 17 species in North America; 

 only one in our region. 



1. Didymodon recurvirostre [Dickson] New Combination. 

 ( D. rubellus Bryologia Europ^a ; Barbula rubella Mitten ; 



Weisia recurvirastra Hedwig). 



Cespitose in large, soft patches, bright green above, rusty- 

 red below ; stems erect, branched, usually 2-5 cm. high, radicvi- 

 lose below ; leaves when dry flexuous and somewhat curled, 

 when moist somewhat recurved-spreading from the ap- 

 pressed and whitish base, narrowly lance-linear, the comal 

 longer, abruptly acute, margin narrowly revolute to near apex, 

 apex obscurely denticulate ; costa either ending in the apex 

 or minutely apiculate-excurrent ; basal leaf-cells elongate, rec- 

 tangular, pellucid, medium-walled, the median and upper 

 much smaller, papillose, rather obscure, quadrate ; perichsetial 

 bracts long-sheathing : seta long, red, slender, sinistrorse ; 

 capsule erect, oblong-cylindric, becoming reddish-brown, 

 smooth ; annulus fragile, revoluble ; peristome-teeth 16, united 

 at base into a very low membrance, linear from a wider base, 

 nodose-articulate, reddish, minntely roughened, with the 

 median line but rarely divided ; lid short, obliquely conic- 

 rostrate ; spores mature in summer or in early autumn : paroi- 

 cous or synoicous. 



On wet, usually calcareous rocks, stones, walls, etc., 

 widely distributed in the Old World and, in North America, oc- 

 curring from Greenland to Alaska and south to the northern 

 United States. Although not yet recorded from our region 

 tlys species is to be expected here. 



8. BARBULA Hedwig. 

 Dioicous ; paraphyses filiform : more or less slender and 

 densely and deeply cespitose, the tufts green to brownish : 

 stems with central strand, thickly-leaved, forked ; leaves erect- 

 spreading, rarely recurved-squarrose, keeled, oblong to pro- 



