HYPNUM. 451 



B. HARPIDIUM. Plants usually tall and robust, often 

 ■erect, more or less pinnately branched. Leaves falcato-secund or 

 ■circinate, longly and gradually acuminate, with a single nerve 

 reaching above half-way and often nearly or quite to the apex ; 

 cells linear, often very long and vermicular, usually much dilated 

 at angles ; paraphyllia often present. Leaves mostly large. 

 Plants more or less aquatic. 



C. DREPANIUM. Plants prostrate or ascending, more or 

 less regularly pinnate. Leaves usually small, strongly falcate or 

 circinate, rarely almost straight but strongly homomallous, 

 nerveless or with two faint nerves, longly and acutely acuminate. 

 Plants rarely aquatic. Paraphyllia few or none, rarely abundant. 



D. LIMNOBIUM. Usually procumbent or ascending, of 

 soft, flaccid texture, variously branched. Leaves usually secund 

 but not strongly falcate, wide, obtuse or apiculate, rarely 

 tapering to a short point, never finely and longly acuminate; 

 nerve double or none, very rarely single. More or less aquatic, 

 on wet rocks. 



E. CALLIERGON. Plants erect or procumbent, usually 

 slightly branched only, or sub-pinnate. Leaves imbricated all 

 round, rarely secund, usually large, broad, glossy, obtuse or only 

 apiculate, nerve single or double. Terrestrial or bog plants, tall 

 and often robust. 



( Leaves sharply acuminate, acumen often long and narrow 2 



i-j Leaves very shortly pointed, or obtuse or apiculate, or with short, bluntish 

 ( acumen 5 



/Nerve single 3 



\ Leaves nerveless, or shortly 2-nerved 4 



/Leaves squarrose or spreading (rarely more or less secund) A. Campylium 



■^Leaves falcato-secund or circinate B. Harpidium 



/Leaves squarrose-divergent A. Campylium 



^\Leaves secund, falcate, or circinate C. Drepanium 



Ls. wide, soft, flaccid, usually secund ; on wet rocks, etc D. Limnobium 



Ls. firm, patent or imbricate ; usually in bogs or on the ground ...E. Calliergon 



A 



A. CAMPYLIUM. 



Leaves more or less ovate-acuminate, acutely pointed, 

 divergent or squarrose when dry, or secund, not strongly falcate. 



[The only species in this Section which have the leaves more 

 or less erecto-patent or secund, not squarrose, viz. H. riparium 

 and H. polygamum, always have a long, single nerve]. 



