50 American Midland Naturalist Monograph No. 6 



cylindric, sometimes sulcata; peristome with a basal membrane, the 16 teeth 

 mostly cleft to the base or nearly so into two linear-filiform portions, papillose, 

 rarely weakly twisted to the left; articulations not projecting dorsally, some- 

 imes coupled at the base of the teeth; annulus mostly serrate, revoluble; oper- 

 culum mostly obliquely conic; calyptra reaching to below the middle of the 

 capsule. 



A cosmopolitan genus of about 50 species, mostly growing on soil, about 

 10 species in North America, 3 of these occurring in our region. 



Key to the Species 



A. Dioicous: leaf-margins more or less recurved; seta castaneous B 



A. Autoicous: awn serrulate; seta bright yellow 3. D. pallidum 



B. Capsule somewhat unsymmetric, subsulcate, somewhat cernuous 1. D. lineare 



B. Capsule symmetric, smooth, erect 2. D. pusilluin 



1. DiTRICHUM LINEARE (Sw.) Lindberg 



(D. tortile var. vaginans Grout; Trichostomum vaginans Sullivant; 

 Leptotrichum vaginans Schimjjer; Ditrichum vaginans Hampe ) 



Plate IX 



Densely cespitose, yellowish-green, lustrous: stems erect, ascending, about 

 5 mm. high, usually with erect terete sterile branches, sometimes up to 1.5 cm 

 high; leaves 1-1.5 mm long, close, erect-appressed when dry, not much spread- 

 ing when moist, from an ovate concave base narrowed to a linear deeply 

 canaliculate acumination, margins narrowly recurved, usually entire; costa 

 strong, percurrent or rarely excurrent, comprising from one-third to one-half 

 of the width of the acumination; upper leaf-cells rectangular, mostly about 2:1, 

 rather dense and incrassate, smooth, the basal larger, elongate-rectangular up 

 to 6-8:1, moderately thin- walled, sub-hyaline or yellowish; perichastial leaves 

 larger, convolutely sheathing, above narrowing abruptly into a linear-subulate, 

 canaliculate, entire acumination, the basal cells larger and laxer than in the 

 stem- leaves: seta erect, flexuous, lustrous, yellowish to brownish, sinistrorse, 

 about 1-2 cm long; capsule brownish, about 1.5 mm long, narrowly to oblong- 

 cylindric, rounded at base, little changed when old; lid about one-fourth the 

 length of the urn, conic-rostellate obliquely, castaneous; annulus 2-3-seriate, 

 wide; peristome-teeth linear subulate, imperfect, forked to the base or often 

 united above, or irregularly cleft, deep castaneous, articulate; exothecial cells 

 yellowish-incrassate, irregularly oblong to rectangular, the 4 or 5 uppermost 

 rows much smaller, rounded and obscure; calyptra cucullate, covering about 

 one-half of the capsule; spores yellowish, smooth, about .01 5-. 018 mm, ma- 

 turing in late fall or winter. 



Usually on sandy soil in hilly or mountainous districts. In Europe, and 

 in North America, from Maine to Missouri and North Carolina. 



Not common in our region. Allegheny Co.: Powers Run, September 14, 1905 (fig- 

 ured). O.E.J, and G.E.K.; Wildwood Road, March 29, 1908. O.E.J, and G.K.J.; 

 Thornhill, December 29, 1908. O.E.J. Fayette Co.: Fort Necessity. H. N. Mozingo. 

 April 1, 1945. McKean Co.: West Branch, September 6, 1896 D.A.B. Westmore- 

 land Co.: One mi. n. of Darlington. C.M.B. Oct. 7, 1944. 



