244 American Midland Naturalist Monograph No. 6 



E. Leaves otherwise C 



C. Costa single and reaching midleaf or beyond D 



C. Costa none or short and double E 



D. Leaves less than 1 mm long 4. H. Closteri 



D. Leaves more than 1 mm long 1. H. luridum 



E. Leaves entire, concave, often sub-tubulose above H. luridum 



E. Leaves denticulate or serrulate towards apex F 



F. Leaves widely spreading; costa single, reaching to midleaf or above 



4a. H. Closteri f. serrulatum 



F. Costa none, or short and double or forked G 



G. Terminal leaves secund; stems and branches rather julaceous; alar cells suddenly in- 

 flated forming distinct auricles 2. H. eugyrium 



G. Stems and branches attenuate and stoloniferous at ends; alar cells only somewhat 



enlarged, rectangular to quadrate; leaves sub-clasping 6. H. novae-caesareae 



\. Hygrohypnum luridum [Hedwig] Jennings 



(Hypnum palustre Hudson; Amblystegtum palustre Lindberg; Hypnum 

 luridum Hedwig; Calliergon palustre Kindberg) 



Yellowish-green, or dark -green, irregularly cespitose in low patches: stems 

 denuded below, long, divided irregularly, the branches erect to ascending, often 

 more or less hooked at the tip; leaves close, either imbricated or more or less 

 falcate-secund, always concave, the margins strongly incurved towards the 

 summit, narrowly oval- to broadly ovate-oblong, entire, about 1-L5 mm long, 

 the apex variable, either obtuse or acute or rounded and apiculate; costa usually 

 single or forked and reaching about half way up the leaf, but variable; leaf- 

 cells rather lax, about 5-10:1, usually linear-rhomboid, rather opaque, some- 

 what shorter towards the apex and towards the base, the alar few, quadrate, 

 sub-opaque, somewhat inflated, forming small, ill-defined auricles which are 

 somewhat decurrent: seta about 1-2 cm long; capsule oblong or oval-oblong, 

 orange-brown, arcuate, rather short and thick, more or less horizontal, dark 

 when dry, exannulate: lid orange-yellow, conic, obtuse to apiculate; peristome 

 normally hypnoid, teeth yellowish, segments scarcely carinately cleft, a little 

 longer than the 2 or 3 cilia; spores mature in summer. 



On wet, cold rocks, where often overflowed, especially in calcareous dis- 

 tricts: Europe, Asia, and the northern United States and Canada, south to 

 New Jersey and Pennsylvania. 



Rare in our region. Huntingdon Co.: T. C. Porter. (Porter's Catalogue). Mc- 

 Kean Co.: D.A.B. (Porter's Catalogue) 



2. Hygrohypnum eugyrium (Brvologia Europaea) Loeske 



{Hypnum eugyrium Bryologia Europaea; Amblystegium eugyrium Lindberg; 

 Calliergon eugyrium Kindberg) 



Widely cespitose in low, dense, usually sand-filled tufts, lustrous, green to 

 reddish to brownish: stems prostrate, often leafless below; branches numerous, 

 erect or procumbent, usually from 0.5-1.0 cm long; leaves wide -spreading when 

 moist, distinctly falcate-secund towards ends of branches, when dry imbricate- 

 erect and concave, thus giving the branches a turgid appearance, oval-oblong 

 or lance-oblong, narrowed to the base, slightly denticulate towards the shortly 



