HYPNACEAE IO3 



HYPNUM L. (Plate XII.) 



Plants usually more or less regularly pinnately branched, 

 often plumose in appearance. Leaves falcate- secund and in 

 most species apparently arranged in two rows, giving the stems 

 a somewhat flattened appearance on one side (usually the upper) 

 and a bristly appearance on the opposite side. Leaves in most 

 cases long acuminate; costa short and double, or lacking entirely; 

 leaf cells linear-flexuose, 4-20: I, shorter at base; alar cells 

 more or less plainly differentiated, often enlarged, hyaline or 

 colored. Paraphyllia present in all our species, few or found 

 only in axils of branches in some cases. Central strand in stem 

 usually present, but few-celled. Capsules subcylindric, more or 

 less curved and cernuous; peristome perfect (excl. H. tennirostris). 



Most of the mosses of this genus have a very similar appear- 

 ance, due to the leaf arrangement described above and the 

 regularly pinnate and two-ranked branching. Exceptions are 

 Haldanianum with its irregular branching; leaves equally spread- 

 ing, not falcate. H. patientiae, H. pratense and forms of H. 

 cupressijorme are irregularly pinnate. The species grow on all 

 sorts of habitats but many have a marked preference for de- 

 caying wood. H. imponens is one of our most common and 

 typical species. Its capsule, however, is more nearly straight and 

 erect than in most species. 



Key 



1 — Alar cells inflated, pellucid, hyaline or colored. (Forms of cupressi- 

 forme may be sought here) 2 



Alar cells scarcely inflated, often small and quadrate (fertile and 



curvifolium may be sought here) 11 



2 — Leaves not falcate or secund 3 



Leaves secund, usually strongly falcate-secund 4 



3 — Leaves ovate, short-acuminate; inflated alar cells numerous, forming 



distinct auricles Haldanianum 



Leaves ovate-lanceolate, long and slenderly acuminate, not auricled; 



differentiated alar cells few, not much enlarged pratense 



4 — Leaves entire or serrulate above only 5 



Leaves strongly serrate above; inflated alar cells very conspicuous. ... 9 

 5 — Inflated alar cells numerous and conspicuous; capsules plicate when 



dry patientiae 



Inflated alar cells rather few 6 



6 — Not regularly pinnate; habit of Plagiothecium pratense 



Regularly pinnate 7 



