OF WESTERN PENNSYLVANIA 111 



Avhen dry imbricate-appressed, very concave, oblong-oval to 

 rather widely ovate, 1-1.5 mm. long, plane-margined, at the 

 apex abruptly terminating in a long, flattened, finely denticu- 

 lated hair, which is decurrent along the upper margin of the 

 lamina, and is often longer than the lamina ; the smaller lower 

 leaves acuminate but without the hair-point ; costa narrow, 

 ending in the apex ; basal leaf-cells quadrate, except a few rec- 

 tangular ones near the costa, the upper smaller and rounded, 

 all incrassate, non-sinuose, the upper quite chlorophyllose : 

 seta erect ; capsule included, elliptic, broadly oblong, brown- 

 ish smooth when dry ; annulus large ; lid conic-rostellate, 

 short, peristome-teeth cleft to about the middle, cribrose be- 

 low, castaneous-pellucid ; calyptra mitrate, lobed ; spores ma- 

 ture in spring. 



On rocks, mainly npn-calcareous, often granite or sand- 

 stone, almost cosmopolitan. In North America from Penn- 

 sylvania to Minnesota, Kansas and the Pacific States. Rare in 

 our region. 



Blair : Tyrone, T. P. James. (Porter's Cata- 



logue). 



3. RHACOMITRIUM Bridel. 



Dioicous : robust plants, loosely and widely cespitose, the 

 mats green to yellowish or blackish-green : stem without cen- 

 tral strand, procumbent to erect, radiculose at the base only, 

 uniformly foliate, often with numerous short branches giving 

 the shoot a nodose appearance ; leaves spreading to recurved- 

 spreading or sometimes secund, when dry appressed, from an 

 ovate to oblong base mostly lanceolate to lance-linear, more 

 or less long-acuminate, often piliferous, sometimes Ungulate 

 and obtuse, margins sometimes 2-layered and sometimes re- 

 curved ; costa mostly broad, flat, and complete ; cells nearly all 

 with sinuose walls, often papillose, towards the base or some- 

 times all over linear : seta long, straight, rarely curved, twisted ; 

 capsule erect, oblong to cylindric, narrow-mouthed, smooth ; 

 annulus broad, curling off ; teeth united at the base but most- 

 ly cleft deeply into 2 (-3-4) filiform divisions, often very 

 long, trabeculate; spores small; operculum conic with a long 

 -lubulate apex from one-third to more than the length of the 

 urn; calyptra mitrate. lobed, not folded, subulate-rostrate, 

 glabrous or rough. 



A world-wide genus of 88 species, mostly on siliceous 

 rocks ; 23 species in Nortli America, probably 3 species in our 

 region. 



Key to the Species. 

 a. Upper leaf-cells quadrate, lower ones linear; shoots not appearing 

 nodose by arrangement of short lateral branches. 



b. 



