86 HYPNACEAE 



(5) The Velutinum group including B. velutinum, B. erythror- 

 rhizon and a number of western species, characterized by small 

 .-ize and in our species by somewhat secund leaves. 



Key 



r — Costa percurrent or nearly so populeum 



Costa extending Yr-% the length of the leaf 2 



2 — Seta sm ooth 3 



Seta rough above, smooth below 9 



Seta rough throughout 10 



3 — Capsules erect and symmetric or nearly so, cilia of peristome rudi- 

 mentary or lacking 4 



Capsules more cr less cernuous and inclined, unsymmetric, cilia 



well developed 5 



4 — Plants very slender, leaves rarely more than 0.7 mm. long, cyrtophyh 'urn 

 Plants with the facies and size of B. oxydadon; leaves 1-1.6 mm. 



long acuminatum 



5 — Capsules suberect, 3-4: 1 oxydadon 



Capsules strongly inclined, and unsymmetric, 2-3: 1 6 



6 — Leaves not plicate or striate; stem leaves gradually narrowed from 



base to apex ; acutum 



Leaves plicate or striate 7 



7 — Stem leaves lanceolate, 0.6 mm. broad at base, gradually and evenly 



narrowed from base to apex flexicaule 



Stem leaves ovate, at least 1 mm. broad at base, more abruptly nar- 

 rowed to a slender acumination 8 



8 — Stem leaves ovate-lanceolate, 2-2.5 by 0.8-1. 1 mm., median leaf 



cells 10:1 salebrosum 



Stem leaves triangular-ovate, 1.2-0.8 mm., median cells 4-6: 1 . .digastrum 

 9 — Leaves plicate, long acuminate, branch leaves strongly serrate, .campestre 

 Leaves not plicate, shorter-acuminate branch leaves entire or serrate. 



plumosum 

 10 — Secondary stems often dendroid, stem leaves ovate and very short- 

 pointed with enlarged and inflated alar cells rivulare 



Not dendroid, stem leaves slenderly acuminate 11 



II — Slender; leaves somewhat secund, in most American plants, stem 



leaves lanceolate velutinum 



Robust; leaves not secund, stem leaves ovate to triangular-ovate. ... 12 

 I2 — Complanate-fcliate like a Plagiothecium; leaves cordate-triangular 

 and strongly and widely decurrent; cilia of inner peristome ap- 



pendiculate Starkei 



Not flattened; leaves ovate and less strongly decurrent; cilia not ap- 

 pendiculate rutabuium 



B. acuminatum (Hedw.) Kindb. "Centreport, Sanial," 

 Flora L. Id.; Grant City, S. Id., E. G. B., Bx!; Closter, N. J., 

 Austin, Bx!; Yonkers, Southworth, Bx! Autumn. 



