DICRANUM. 115 



19. Dicranum asperulum Mitt. (Dicranum aristatum 



Schp., Syn.) (Tab. XIX. E.). 



In paler, more silky tufts than the last species, less robust 

 and less glossy; stems very slender. Leaves erecto-flexuose or 

 falcate, from an oblong-lanceolate sheathing base, rather longer 

 in proportion to the length of the leaf, narrowed to a fine 

 channelled setaceous subula ; margin from the middle of the leaf- 

 base upwards densely and strongly denticulate ; nerve about \ 

 width of base, at back above with several serrate ridges, 

 excurrent into a densely spinulose arista; angular cells lax, 

 hyaline, reaching to the nerve ; above rather laxly rectangular, 

 chlorophyllose, narrower towards margin, decreasing in width 

 upwards, in the upper part resembling those of the last species 

 but shorter and less obscure. Seta straight, capsule oval- 

 cylindric, erect. Peristome teeth cleft half-way. 



Hab. Sandstone rocks on mountains. Rare. Sterile in Britain. 



A somewhat variable plant, and occasionally coming very near the last species ; 

 usually however the much closer denticulation of the margin, from very near the base 

 of the leaf, and the very rough arista, together with the more slender habit and 

 smaller, less regularly falcate leaves, will distinguish it. The auricles also are some- 

 what wider and more distinct. There is a tendency towards the same peculiarity in 

 the basal areolation, but it is not nearly so marked. It resembles Dicranodontium 

 longirostre even more closely, but the same characters will usually separate the two, 

 and the auricles of the latter plant are more distinct and the nerve rather wider. 



This and the preceding species resemble Dicranodontium in the habit and the 

 leaves, and have been included in that genus ; but the capsule and peristome are quite 

 dicranoid. 



20. Dicranum longifolium Ehrh. (Tab. XIX. F.). 



Slender, in pale, bright green, soft, silky tufts, stems ascend- 

 ing, here and there geniculate. Leaves long, falcato-secund, 

 hardly crisped when dry, from a lanceolate base longly subulate- 

 setaceous, tubular above ; nerve very broad, ]4 or more width of 

 base, widening a little just above the line of insertion, occupying all 

 the upper part of the leaf, remotely denticulate above at back, 

 more closely at apex, in section of three rows of nearly equal, 

 empty, hyaline cells ; margin slightly denticulate above ; angular 

 cells lax, hyaline or brownish, reaching to nerve, above hexagonal- 

 rectangular, decreasing in size upwards, to narrowly elliptical or 

 linear. Capsule erect, straight or incurved, cylindric, smooth. 



Hab. Mountains, rare. Sterile in Britain. 



Distinct from all the other British species in the great width of the nerve, render- 

 ing the leaf- bases pale and shining, and therefore not likely to be taken for any other 

 Under the microscope ; in habit however it is mtich like forms of D./uscescens, and 



