496 HYPNACEAE. 



Family 13. HYPNACEAE Hanipe. 

 HYPNUM FAMILY. 



Plants growing in loose or dense tufts, seldom floating. Stems usually 

 decumbent and rooting, sometimes erect; branches regularly pinnate or 

 irregular. Leaves straight or curved, erect, spreading or secund, usually 

 symmetric ; vein either lacking, single or double ; cells mostly much longer 

 than wide, smooth or papillose, those of the basal angles often different in 

 shape and size. Pedicel more or less elongated and exserted; capsule 

 mostly horizontal, often curved and unsymmetric; peristome double; its 

 segments keeled ; cilia usually present ; spores small. A large family, widely 

 distributed in all parts of the globe, composed of about 37 genera with 

 over 960 species. 



Cells of leaves smooth. 



Vein single, ending in the middle of the leaf. 1. Amblyategium. 



Veins lacking or short and double. 



Leaves uniform and regular; alar cells enlarged. 2^ Isopterygium. 



Leaves of two kinds, the lateral ones broader and 



shorter : alar cells not enlarged. 3. Vesicularia. 



Cells of leaves papillose. 



Papillae single at the ends of the cells. 4. Mittenothamnium. 



Papillae several along the middle of the cells. 5. Ta-xithelium. 



1. AMBLYSTEGIUM Bruch & Schimp. Bryol. Eu. 55-56: 1. 1853. 



Plants usually growing in moist situations. Stems irregularly branched; 

 branches slender; leaves symmetric., spreading; vein single; cells smooth, not 

 much longer than wide. Pedicel erect, smooth ; capsule usually curved ; calyptra 

 cueullate; lid conic; annulns present; peristome double. [Greek, referring to 

 the blunt lid.] A genus of 47 species, widely distributed in America and 

 Europe. Type species: Hypnum riparium L. 



1. Amblystegium Sipho (Beauv.) E. G. Britton. 



Hypnum Sipho Beauv., Prodr. Aetheog. 70. 1805. 



Amblystegium riparium floridanum Ken. & Card. Bot. Gaz. 14: 98. 1889. 



Plants in thin mats on damp ground in shade. Stems creeping, very slen- 

 der, more or less branched ; leaves distant, shrivelled and twisted when dry, 

 narrowly lanceolate, acuminate, up to 1 mm. long by 0.4 mm. broad, the mar- 

 gins entire, the vein ending in the middle of the leaf; base narrow; alar cells 

 oblong or square ; upper cells 4 times longer than wide ; perichaetial leaves 

 erect, pale and faintly veined, with more slender points. Autoicous; pedicel 

 about 1 cm. high, red at base, paler above; capsule short, only about 1 mm. 

 long, horizontal and curved ; lid conic ; peristome double, yellow ; teeth paler 

 at apex, inner segments split along the keel ; spores small, smooth, ripe in 

 spring. 



In sink-hole, Eleuthera : southern' United States. AMBLYSTEGIUM. 



2. ISOPTERYGIUM Mitt. Journ. Linn. Soc. 12: 21. 1869. 



Plants usually rather small. Stems decumbent and irregularly branched; 

 leaves somewhat flattened, small and crowded, usually symmetric ; vein short 

 and double or none; pedicel erect; capsule erect or horizontal; lid conic or 



