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gen. thick. Stem us. not pinnate, r. witli paraphyllia. Leaves 

 sometimes not falcate. 



III. Harpidiiini. Leaves gen. not mamillose, in few species 

 striate; cells gen. narrow exc. the gen. hyaline or sometimes 

 not distinct alar; costa gen. not thick. Stem us. not radiculose, 

 sometimes pinnate; paraphyllia wanting. Leaves (in few species) 

 sometimes not falcate. 



aa. Alar leaf-cells not distinct. 



1. Riparia. Leaves gen. straight subdistichous; lower basal 

 cells nearly uniform subquadrate in 2 — 5 rows. Monoecious 

 often fruiting. Stem often radiculose. — Growing princ. on 

 logs in water. 



2. Revolventia. Leaves falcate; lower basal cells gen. few, 

 short and dilated. Sometimes monoecious. Stem not radiculose. 

 Leaves often reddish. — Growing in swamps. 



bb. Alar leaf-cells distinct. 



3. Adunca. Leaves not r. straight (princ. in H. fluitans, H. 

 exanmdatum and H. elodes), r. plicate when moist. Us. dioe- 

 cious, not often fruiting. Stem r. radiculose. Leaves sometimes 

 (princ. in H. exanmdatum) reddish. — Growing in swamps. 



4. Uncinata. Leaves us. falcate, gen. plicate. Us. monoecious, 

 often fruiting. Stem r. radiculose. Leaves greenish. — Growing 

 on dry stone?, base of trees and dry earth, r. in water. 



b. Leaves recurved at borders below, subundulate when dry. 



IV. Rliytidiuni. Leaves faintly rough above at both sides, 

 falcate or nearly straight; alar (angular) cells small very nume- 

 rous. Stem without rhizoids and paraphyllia. 



B. Leaves with short double or indistinct (in H. resupinatum 

 sometimes simple) costa, falcate or (sometimes in H. ciipressi- 

 forme) straight, sometimes (in subg. Cupressina and Gampylo- 

 phyllum) recurved at borders. Stem sometimes (in Cupressina) 

 with paraphyllia. Dioecious or monoecious. 



V. Pseudo-Hylocomium. Leaves spreading when dry, large 

 denticulate not circinnate, us. plicate below; special alar cells 

 not defined. Stem not or irregularly pinnate, not creeping. 

 Dioecious. 



VI. Campylophylluni. Leaves spreading when dry, small 

 fiiintly denticulate subcircinnate not plicate; alar cells small 

 distinct. Stem pinnate creeping. Monoecious. 



VII. Drepanium. Leaves not spreading when dry, large nearly 

 entire not circinnate, sometimes striate or plicate; alar cells 



