264 A MANUAL OF MOSSES 



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q. Stem-leaves turgidly imbricate and secund, rugose, narrowly lance- 

 acuminate from a broadly oblong base, glossy: apex serrate: cilia 

 t\vo; annulns present. 13. Rhytidhim. 



q. Stem-leaves close, or loosely imbricate, not secund, broadly ovate 

 or rounded and with an obtuse apex, olive or grayish-green, apex 

 finely crenulate: cilia three; annulus none. 



15. Hy[> num. 



r. Alar cells little or not at all differentiated; plants distantly and 

 irregularly pinnate; leaves squarrose or spreading and secund. 



12. Rhytidiadclphiis. 



r. Alar cells distinctly differentiated; plants closely pinnate; leaves 

 circinate-secund. 11. Ctenidium. 



s. Plants large, to 15 cm. tall, closely and regularly pinnate; leaves 

 linear-acuminate from a broadly ovate base, stem-leaves plicate, 

 falcate-secund: cilia 3 or 4. 16. Ptil'mm. 



s. Plants robust to quite slender, simple or pinnate, mostly irregu- 

 larly pinnate; leaves ovate- to cordate-lanceolate, shortly to slen- 

 derly acuminate, generally circinate-secund in two series. 



17. St crcadon-, 



t. Leaf-cells very narrowly prosenchymatous, alar cells mostly 

 not differentiated; leaves oblong to linear, short-pointed, ovate 

 to linear-lanceolate, acute to long-acuminate or piliferous. 



18. Isopterygium. 



t. Leaf-cells wider, alar cells broader proportionally, hyaline and 

 thin-walled: leaves broadly lanceolate to oval, more or less 

 long-acuminate. 19. Plagiotlicciuin. 



1. AMBLYSTEGIUM Bryologia Europzea. 



Autoicous : usually more or less slender, in thin and spread- 

 ing mats : stem creeping to ascending or even erect, irregularly 

 to pinnately branched, the branches mostly more or less erect ; 

 stem-leaves similar to branch-leaves, erect-spreading to squar- 

 rose, mostly shortly decurrent, cordate- to ovate-lanceolate, 

 long-acuminate, rather concave, non-plicate, entire to serrate ; 

 costa thin, simple, reaching to the middle of the leaf or beyond, 

 rarely complete ; cells parenchymatous and rectangular to 

 elongate-prosenchymatous and hexagonal, rarely linear, 

 smooth, the alar quadrate to rectangular, the inner perichsetial 

 leaves erect, broadly lanceolate, mostly costate : seta long, 

 thin, reddish to castaneous, flattened when dry; capsule, from 

 an erect collum, curved to oblong or cylindric, smooth when 

 dry, constricted below the expanded mouth, annulate ; peris- 

 tome-teeth basally confluent, yellow to orange, lance-subulate, 

 bordered, dorsally cross-striate, above pale and papillose, 

 densely trabeculate below; inner peristome yellowish, basal 

 membrane high ; segments carinate, entire, or slightly gaping 

 along the keel ; cilia complete, nodose, rarely appendiculate ; 

 lid conic, obtuse to acute ; spores small. 



A genus of about 50 species occurring mainly in temperate 

 regions, on various sub-strata; about 20 species in North 

 America ; six in our range. 



