Jennings: Manual of Mosses — 7. Grimmiaceae 95 



B. Teeth undivided, cribrose, cleft in upper half, or none; branches! as high as the 



stem; basal leaf-cells mostly smooth-walled 2. Grimmia 



B. Teeth divided almost to the base into two filiform divisions; branches irregular 



short; basal leaf-cells with nodulose or sinuose walls 3. RhacomitTtum 



1. Ptychomitrium Fuernrohr 



Autoicous: cespitose in loose yellowish-green to brownish or blackish 

 cushions; stem with central strand, erect or ascending, radiculose at the base, 

 thickly-leaved; leaves long, narrow, the points not hyaline, crispate when dry, 

 spreading when moist; costa strong, percurrent or ending below the apex; cells 

 not with sinuose walls, smooth, upwards small and rounded-quadrate, below 

 linear to more or less loosely rectangular; perichaetial leaves not sheathing: seta 

 straight, more or less elongate, mostly two or more to a perichaetium; capsule 

 smooth, erect, symmetric, mostly oval to oblong-elliptic; annulus wide, decidu- 

 ous, rarely none; peristome inserted below the mouth; teeth 16, papillose, 

 usually deeply divided into two subulate prongs, trabeculae more or less dis- 

 tinct; spores small; operculum conic with a long, fine, straight beak; calyptra 

 campanulate, plicate and lobed, reaching about halfway down the capsule. 



A widely distributed genus of 62 species, of which at least 9 occur in 

 North America and one in our region. Occurring on rocks and stones, — 

 rarely on trees. 



1. Ptychomitrium incurvum (Muhlenberg) Sullivant 



Plate LXIII 



Densely cespitose, dark green to brownish: stems about 5 mm high, erect; 

 leaves erect-spreading when moist, sometimes incurved, twisted-crispate when 

 dry, the lower small, increasing in size upwards, linear-lanceolate, obtuse, thick, 

 opaque, the margin plane; costa broad, ending in apex; basal leaf-cells rectangu- 

 lar, pellucid, the upper m.uch smaller, rounded to quadrate, incrassate, dense; 

 seta about 2-3 mm high, erect; capsule erect, oval; peristome-teeth 16, long- 

 subulate, articulate, papillose; lid erect, conic-subulate, about as long as urn; 

 calyptra long-rostate, mitrate, plicate-lobed to base of beak, covering a little 

 more than half of the urn; spores mature in spring. 



On more or less exposed calcareous rocks from Connecticut to Georgia 

 and Texas. Not uncomm.on in eastern Pennsylvania, northern Ohio, and 

 western New York. 



Westmoreland Co.: On limestone rock, l'/2 miles east of Hillside. Chestnut Ridge, 

 C.M.B. May 30. 1936 (figured). 



2. Grimmia Ehrhart, Hedwig 



Autoicous or dioicous: forming cushions and mats, slender, often hoary 

 by reason of the hyaline leaf-apices: stem erect or ascending, mostly with a 

 central strand, radiculose mainly at the base, thickly-leaved; leaves imbricate 

 when dry, rarely crispate or spirally appressed, spreading to recurved-squarrose 

 when moist, lower often small and bract-like, the upper often suddenly larger, 

 often hyaline-piliferous, carinate, concave, sometimes canaliculate, mostly 



