73 American Midland Naturalist Monograph No. 6 



K. Divisions of peristome distinctly sinistrorsely twisted ...6. Torlella 



L. Peristome-teeth 16, more or less 2-cleft or perforate, erect or', dextrorsely ascending 



7. Didynwdon 



L. Peristome-teeth 32, filiform, strongly twisted sinistrorsely 8. Barbula 



M. Cleistocarpous; capsule spherical to oval, apiculate; leaves ovate to broadly lan- 

 ceolate 10. Phascum 



M. Operculate N 



N. Peristome-teeth 16 or none O 



N. Peristome-teeth 32, filiform, sinistrorsely twisted, with a high basal membrane; 



leaves oblanceolate to obovate or spatulate 13. Tortula 



O. Peristome-teeth none, or rudimentary from a low basal membrane 11. Pottia 



O. Peristome-teeth small, separate to the base, more or less divided into two or three 



slender prongs 12. Desmatadon 



I. AsTOMUM Hampe 



Autoicous, rarely polyoicous: small, gregarious to cespitose, dull green: 

 stem with a few-celled central strand, radiculose, thickly foliate; upper leaves 

 tufted, when dry mostly crisped, keeled, from a broad base lanceolate to sub- 

 ulate-lanceolate, margin plane to involute, entire; casta strong, percurrent or 

 excurrent; leaf-cells in upper part of leaf small, rounded-quadrate, papillose 

 both sides, the lower cells elongate-quadrangular, thin-walled and hyaline: 

 capsule mostly immersed, almost spherical to oblong-elliptic, m.ostly with a 

 small, elongate-conic op)erculum, which, however, is rarely deciduous; calyptra 

 cucullate, rarely mitrate, smooth. 



A widely distributed genus of 21 terrestrial species; 3 species occurring in 

 North America; 2 (3) species in our region. 



1. AsTOMUM Muhlenbergianum (Swartz) Grout 



(Astomum Sullivantii Schimper; A. crispum Am. Auth.) 

 Plate LXII 

 Densely cespitose, pale to dark green: stem about 5 mm high, usually 

 branched above, erect; leaves numerous, close, when dry crispate, the stem- 

 leaves small, lance-linear, the comal and perichaetial much larger, up to 4 mm 

 long, elongate-linear from a narrowly oblong, concave, whitish base, usually 

 narrowly involute or canaliculate above, the apex abruptly acute; costa strong, 

 acutely and shortly excurrent-mucronate, sometimes upturned so as to make 

 the leaf somewhat cucullate; basal leaf-cells laxly and irregularly lon^-'ectangu- 

 lar, hyaline, upper leaf-cells sub-quadrate, densely chlorophyllose, papillose: 

 seta erect, shorter than the capsule; capsule immersed, ovoid, small, brownish, 

 about 1 mm long; lid finally distinct but not separating from the urn of its 

 own accord, minute, obliquely conic-apiculate to short rostellate; exothecial 

 cells laxly hexagonal to oblong-hexagonal, one to three rows of cells being 

 somewhat smaller at the junction of the lid; calyptra cucullate; spores papil- 

 lose, .021 -.027 mm, mature in spring: autoicous; the immature capsule fully 

 grown by late November. 



In old sandy or clayey fields and along roadsides, principally in non- 

 calcareous districts, temperate Europe, Japan, Algeria, and, in North America, 

 from Saskatchewan to Massachusetts and southward to the Gulf States. 



