98 HYPNACEAE 



removing these, great care must be taken to get all of the leaf 

 as the characteristic swollen alar cells often remain attached to 

 the stems. 



Plants slender to very robust, without paraphyllia (there are 

 a few inconspicuous paraphyllia in D. uncinatas). Leaves 

 falcate-secund to circinate, often forming conspicuous hooks at 

 the ends of the stem and branches, not papillose, nearly always 

 longly and slenderly acuminate; costa single and well developed, 

 reaching well into the upper }/% of the leaf; leaf cells very long 

 and narrowly linear (shorter in forms of aduncus); alar cells in 

 most species enlarged and inflated, forming more or less con- 

 spicuous decurrent auricles; basal cells usually shorter and 

 thicker walled, often porose. Capsules inclined to horizontal, 

 subcylindric and curved, usually somewhat contracted under 

 the mouth when dry, with a perfect hypnaceous peristome. 



Key 



i — Leaves entire (excl. forms of revolvens), somewhat narrowed to the 

 nearly straight insertion, with no enlarged or decurrent alar cells 

 but with a row or two of thick-walled broader and shorter cells 



across the base 2 



Leaves with alar cells distinctly enlarged and inflated ; often decurrent 



or plainly serrate or both 3 



2 — Plants robust, the older portions usually a deep reddish purple; 



stems with a central strand; leaves not plicate revolvens 



Plants as a rule more slender and less deeply colored; central strand 



lacking; leaves plicate vernicosus 



3 — Leaves entire; alar cells usually greatly enlarged and inflated, .aduncus 



Leaves, some or all plainly dentate 4 



4 — Leaves strongly plicate even when moist uncinatus 



Leaves not plicate; alar cells more or less inflated fluitans 



D. aduncus (Hedw.) Warnst. Infrequent except in N. J. 

 Austin gives varieties from Little Falls, Muse. App. 405, var. 1, 

 which is probably var. gracilescens; No. 407 which is labeled 

 var. gracilescens is not this var. It may be var. aquaticus. 

 Austin calls this form common. Var. gracilescens (Sch.) is 

 reported also from Orient, L. Id., Latham. Summer. 



Subspecies Kneifii (B. & S.) Warnst. "Sunken places about 

 Closter, N. J.," Muse. App. 411; New Dorp, S. Id., near Mo- 

 ravian Cemetery!! 



