Jennings: Manual of Mosses — 5. Pottiaceae 91 



A. Leaves obtuse to short apiculate B 



B. Leaves bordered with a band of lighter colored, elongate cells (D. Porferi) 



B. Leaves not bordered L D. obtusijoLus 



I. Desmatodon obtusifolius (Schwaegrichen) Jur. 



{Desmatodon arenaceus Sullivant; D. ohioensis Schimper; 

 Didymodon areriaceus Kindberg) 



Plate XVII 



Gregarious to loosely cespitose, bright yellowish-green: stems short, in our 

 specimens about 3 mm. long, radiculose at base; leaves erect-spreading when 

 moist, crisped when dry, very small below but increasing to form a comal 

 tuft above, from ovate to lance-ovate, the comal 2-3 mm long, bluntly acute, 

 short-apiculate, the margin entire and more or less revolute; costa strong, 

 reaching the apex or extending into the apiculation; upper leaf-cells opaque, 

 incrassate, papillose, from rounded to hexagonal or quadrate, towards the base 

 of the leaf becoming elongate, thin-walled and hyaline: seta erect, 6-8 mm 

 high, sub-lustrous, sinistrorse, castaneous; capsule dark-castaneous, oblong, 

 the urn 2-4 mm long; peristome-teeth yellow, slender, divided almost to the 

 base into two slender, minutely-papillose prongs; annulus distinct, revoluble; 

 operculum bluntly and obliquely conic-hexagonal, immediately below the 

 annulus being smaller and incrassate; spores smoothish, yellowish, .01 2-. 01 5 

 mm, mature in spring. 



On sandy soil, rocks, etc., mainly confined to the drainage-system of the 

 Ohio River. 



Rather rare in our region. Crawford Co.: Linesville, May 12, 1908. O.E.J, (fig- 

 ured). Fayette Co.: Along river-bank at Ohio Pyle, September 1-3, 1907. O.E.J, and 

 G.K.J. McKean Co.: Near Bradford. December 15. 1894. D.A.B. 



13. ToRTULA Hedwig 



Autoicous or dioicous, rarely svnoicous or polyoicous: small to robust, 

 in green to brown tufts or cushions: stems mostly with a central strand, below 

 brownish- or red-radiculose, simple or branched; leaves mostly larger at the 

 ends of the shoots, often appearing rosette like, when dry not crispate but 

 somewhat twisted and contorted, when moist erect-spreading, mostly keeled, 

 cbovate or spatulate, rounded at the apex or rarely short-acuate, commonly 

 bordered, usually entire; costa strong, often cylindric, often mucronate-excur- 

 rent or, more commonly, excurrent into a hyaline hair-like awn; upper leaf- 

 cells rounded-hexagonal, loose, chlorophyllose, papillose, grading below into 

 the rectangular to elongate hyaline basal cells: seta long, erect; capsci'e erect, 

 cylindric, symmetric, short-necked, straight or sometimes slightly arcuate; 

 annulus present; peristome single, rarely none, basal membrane low to high, 

 teeth 32, filiform, equally spaced, mostly once to twice dextrorsely wound, 

 papillose and transversely striate, articulate; operculum conic, obliquely ros- 

 trate; calyptra cucullate, reaching to the middle of the urn; spores small. 



A large genus of more than 200 species, widely distributed in the temper- 



