290 American Midland Naturalist Monograph No. 6 



Iste; peristomc-teeth strong, basally confluent, dorsally cross-striate, apically 

 papillate, thickly lamellate; inner fjeristome about the same length, yellow to 

 orange, free, with wide basal membrane, the segments broadly lanceolate, long- 

 acuminate, carinately split and often gaping, cilia complete, nodose to appen- 

 diculate, rarely rudimentary or lacking; lid conic-convex, obtuse to acute; 

 calyptra glabrous. 



A genus of about 225 species, occurring on various substrata, mostly con- 

 fined to temperate regions; at least 12 species in our region. 



Key to the Species 



A. Seta smooth; annulus often present; cilia well-developed B 



A. Seta rough at least in part E 



B. Capsules sub-erect, narrowly cylindric-oblong; usually more than 3 : 1 



1. B. oxycladon 



B. Capsules cernuous, usually less than 3:1 C 



C. Leaves narrowed gradually from base to acuminate ap>ex, non-plicate 5. B. dcutum 



C. Stem-leaves ovate-lanceolate, more or less plicate D 



D. Stem-leaves broad, about 1 mm at base, not falcate-secund 3. B. salebromm 



D. Stem-leaves narrow, about 0.5-0.6 mm at base, very gradually narrowed to the 



apex 4. B. flexicaule 



E. Seta rough only above F 



E. Seta rough throughout H 



F.Costa percurrent or very nearly so 11. B. populeum 



F. Costa ending about in middle of the leaf G 



G. Stem-leaves plicate: cilia non-appendiculate 2. B. campestre 



G. Stem-leaves non-plicate: cilia appendiculate 12. B. flagellare 



H. Cilia appendiculate I 



H. Cilia non-appendiculate J 



r. Costa percurrent or sub-percurrent 8. B. reflexum 



I. Costa distinctly incomplete 9. B. Starkei 



J. Stem-leaves very short-acuminate, alar cells abruptly inflated 7. B. rivulare 



J. Leaves gradually acuminate; alar cells not very abruptly enlarged and inflated K 



K. Slender; leaves lanceolate, often secund 10. B. velutinum 



K. Robust; leaves ovate to lance-ovate, not secund 6. B. rutabulum 



\. Brachythecium oxycladon [Bridel] Jaeger and Sauerb 

 (B. laetum Bryologia Europaea; Hypnum oxycladon Bridel) 

 Plate LXIX 



Cespitose, bright or yellowish-green: stems prostrate, branching unequally 

 and irregularly, the branchlets attenuate at the apex and erect; leaves close, 

 loosely imbricate, ovate in the stem-leaves (2-2.5 mm) and more lance-ovate 

 in the branch-leaves (1.5-2 mm) rather abruptly acuminate, concave, plicate, 

 finely serrulate all around; costa rather narrow, extending about to mid-leaf 

 or somewhat farther; median leaf -cells long, narrow, about 8-10:1, flexuous, 

 the basal more or less quadrate, the alar numerous, small, rather incrassate, 

 the alar portion strongly decurrent: seta about 2.5 cm long, flexuous, flattened 

 and dextrorse when dry; capsule sub-erect, about 4:1, 3-4 mm long, oblong- 

 cylindric, when dry somewhat arcuate and often inclined; lid conic-acuminate; 



