MUSCI PLEUROCARPI. 



Inflorescence gemmiform, produced in the axils of leaves on the 

 main stem, or on the secondary branches, so that the fruit is always 

 lateral. Stem much branched, prostrate, decumbent or less frequently 

 erect, sometimes floating or pendent. 



Fam. 19. HYPNACE^. 



Plants very variable in size and habit, generally procumbent and 

 much branched, pinnate or with the branches irregular. Leaves in 

 many rows, spreading on all sides, or falcate and secund, or complanate, 

 smooth or occasionally papillose, ovate or lanceolate, entire or serrated ; 

 usually with one nerve, sometimes with two nerves, or nerveless, cells 

 prosenchymatous, narrow and vermicular, rarely ovoid and incrassate, 

 those at basal angles usually quadrate and often vesicular or coloured. 

 Calyptra cucuUate, smooth or very rarely somewhat hairy. Capsule on 

 a long seta, more or less incurved and cernuous, rarely regular and 

 erect ; peristome of 16 teeth, lanceolate-subulate, trabeculate, with a 

 zigzag divisural line, lamellose internally, endostome a carinate-plicate 

 basal membrane, with 16 processes and i — 3 more or less perfect cilia 

 interposed between them. 



The vast group of mosses embraced by the Hypnacese has taxed the 

 powers of all bryologists to arrange satisfactorily into genera ; for unlike the 

 acrocarpous division, they possess so much uniformity in habit and structure, 

 that they defy all sharp distinctions, and we have thus to depend on 

 characters of less importance than those used for the acrocarpi, and rely 

 more on natural habit. 



C. Mueller and Hampe maintained one huge genus Hypnum for most 

 of the species, breaking it up into sections or subgenera, depending on 

 the habit or foliage ; Schimper went too far in the opposite direction, and 

 established many genera on trivial differences, such as an obtuse or rostrate 

 operculum. Following Mitten and Lindberg, I have endeavoured to steer a 

 middle course and retained such genera as presented the strongest natural 

 characters and minor sections for groups of allied species. 



The study of these mosses (as indeed of all species), must be carried out 

 in connection with their congeners throughout the world, for in several 

 instances we have in Europe but one or two outlying stragglers of some great 



