54 A MANUAL OF MOSSES 



subulate, imbricated to erect-spreading or secund. when drv 

 mostly a little curved- or straight; costa broad and flat, per- 

 current or excurrent, usually filling the upper part of the 

 acumen: leaf-cells rectangular, more or less prolonged: seta 

 elongate, erect; capsule erect or a little cernuous, symmetric or 

 unsymmetric. sometimes weakly arcuate, mostly ovate to 

 oblong-cylindric. sometimes silicate; peristome with a basal 

 membrane, 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, sometimes coupled 

 at the base of the teeth ; annulus mostly serrate, revoluble ; 

 operculum mostly obliquely conic ; calyptra reaching to below 

 the middle of the capsule. 



A cosmopolitan genus of about 72 species, mostly growing 

 on soil, about 20 species in Xorth America, 3 of these occurring 



n our regon. 



Key to the Species. 



a. Dioicous: perichsetial leaves more or less sheathing. 



b. 

 a. Autoicous. 3. D. pallidnui. 



b. Capsule somewhat unsymmetric, subsulcate. somewhat cer- 



nuous. T. D. I'agiuans. 



b. Capsule symmetric, smooth, erect. 2. D. tortile. 



1. Ditrichum vaginans (Sullivant) Hampe. 



(D. tortile var. vaginans Grout; Trichostoimtm vaginans Sulli- 

 vant; Leptotrichum vaginans Schimper.) 



(Plate V) 



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 spreading 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, compris- 

 ing from one-third to one-half of the width of the acumina- 

 tion; upper leaf-cells rectangular, mostly about 2:1, rather 

 dense and incrassate, smooth, the basal larger, elongate-rectan- 

 gular up to 6-8:1, moderately thin-walled, sub-hyaline or yel- 

 lowish ; perichsetial 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, rlexuous, 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 trie 



