450 hypnacejE. 



The members of this genus are distinguished from 

 Amblystegium by the longer, narrower cells ; from Plagiothecium 

 by the areolation and rarely complanate leaves (one or two species 

 alone having them secund and homomallous as in P. pulchellum) , 

 from Eurhynchium by the non-rostrate beak, etc. ; from 

 Brachythecium by the usually sub-cylindrical, narrower capsule, 

 the linear rarely rhomboid areolation, and the nerve rarely 

 single ; but as in other cases, individual plants, especially when 

 barren, can often only be referred to the right genus by 

 experience. The student, however, will do well to bear in mind 

 that no species with longly acute or acuminate leaves and well- 

 defined single nerve belong to this genus except those of the 

 Sections Harpidium (easily known by the strongly falcate leaves), 

 and two or three species of the Section Campylium. 



In classifying the species of this large genus I have for the 

 most part followed the system employed by Schimper in the 

 Synopsis. It is, however, I think, generally felt that the sub- 

 divisions there are unnecessarily numerous, and I have in one or 

 two cases merged two of his sub-genera into one. Thus under 

 Harpidium I have included all the falcate-leaved species with 

 elongated single nerve and with the angular cells usually dilated, 

 irrespective of the thickness of the nerve ; i.e. I have included the 

 sub-genus Cratoneuron of Schimper ; the nerve in some of the true 

 Harpidium species being equally strong, while in H. sulcatum it 

 is very feeble ; and the presence of paraphyllia and radicular 

 tomentum being equally inconstant. I have also eliminated the 

 sub-genera Ctenidium and Ctenium , placing the two species 

 there included by Schimper, viz., H. molluscum and H. crista- 

 castrensis, under Drepanium, from which they are hardly 

 separable by any important structural detail ; and I have done the 

 same with H . incurvatum, our only British representative of the 

 sub-genus Homomallium. Scorpidium (H. scorpioides) will be 

 found united with Limnobium, and H. (Rhytidium) rugosum 

 placed (following Lindberg) with Hylocomium. I venture to 

 think that by so doing an equally sound basis of classification is 

 arrived at, while the characters on which the Sections, or sub- 

 genera, are based are much more clearly defined and consequently 

 much more easily employed by the student. 



A. CAMPYLIUM. Leaves more or less longly acuminate, 

 usually squarrose-divergent both wet and dry or rarely secund, 

 never strongly falcate nor circinate ; branching irregular or sub- 

 pinnate ; nerve single, varying in length, or none, rarely double ; 

 cells narrow-linear. Plants often small. Paraphyllia none. 



