BRACHYTHECIUM. 



407 



Very variable, but usually not difficult to recognise in the field, by its small size, 

 small and narrow, silky, but not distinctly plicate leaves ; these are usually spreading 

 when dry, which gives the branches a very different appearance from those of B. 

 populeum, which has them commonly terete from the closer imbrication of the leaves ; 

 this, however, sometimes is the case with the present plant, and it then resembles 

 slender forms of Pleuropus sericeus, which of course, however, is very different in the 

 plicate leaves, etc. There is often a resemblance .to Eurhynchium confertum, but 

 that plant has less tapering and less silky leaves, and a long-beaked fruit. 



Several varieties are described, one, var. pralongum B. & S., a marked form 

 with setae over an inch long, and elongated stems ; I have not, however, seen any 

 British records. The var. intricatum Hedw. appears to be only a somewhat marked 

 form of a very common state of this species, and to be connected with the type by 

 numerous and widely-spread links. 



The leaves are more opaque than in most of the previously described species of 

 the genus. 



12. Brachythecium populeum B. &S. (Hypnum populeum 



Hedw. ; H. viride Lam.) (Tab. LIII. D.). 



Slender, in small dense patches, of a bright or more 

 commonly yellowish green ; stems procumbent, divided, with 

 numerous, pinnately arranged, erect or curved branches, which 

 are slender, and more or less terete when dry. Leaves closely- 

 imbricated and erect when dry, or slightly homomallous ; stem- 

 leaves ovate-lanceolate , branch-leaves narrower, lanceolate ; all 

 gradually tapering to a fine, elongated acumen; hardly plicate, 

 shortly decurrent ; margin more or less recurved, in upper half 

 finely denticulate ; nerve strong, very long, reaching nearly to 

 apex ; cells narrow-linear, rather acute, 6-12 times as long as 

 wide ; at base wide, irregularly rectangular, those at the angles 

 more numerous, reaching higher in the leaf, somewhat opaque, 

 often yellowish. Seta rough, usually almost smooth at the base ; 

 perichastial leaves squarrose. Capsule small, oval, gibbous at 

 back ; lid shortly acuminate. Autoicous. 



Hab. Sandy ground, walls, etc., frequent; in some districts common. Fr. 

 winter. 



The narrow, silky foliage, erect and imbricated when dry, and longly acuminate, 

 gives this species a characteristic aspect, much resembling in miniature that of 

 Pleuropus sericeus, by which it may generally be known. It is markedly distinct, too, 

 from nearly all the Hypnacete in the narrow, gradually and longly tapering leaves, 

 with the nerve reaching nearly to apex. Lescurcea rfriVzta differs in the short cells and 

 numerous paraphyllia ; Eurhynchium tenellum in the much more slender habit, very 

 short branches and still narrower leaves, besides the rostrate lid ; and Hypnum elodes 

 in the slender habit and distant, spreading leaves. 



13. Brachythecium plumosum B. &S. (Hypnum plumosum 



Sw. ; H. pseudoplumosum Brid.) (Tab. LIII. E.). 



In large dense patches, robust ; stems prostrate, 2-3 inches, 

 with densely pinnate branches, erect or curved, stout, somewhat 



