Il6 DICRANACE^E. 



is hardly to be recognised certainly by the eye alone, though the leaves are more 

 finely setaceous than in that and most other species. 



D. albicans B. & S. , a continental species, has a still wider nerve, occupying the 

 greater part of the leaf-base ; indeed leaving hardly any margin, and in this respect 

 forming a transition to Leucobryum. 



D. Sauteri B. & S. is described by Braithwaite as British, but its authority is doubtful, 

 being confined to unnamed specimens found in a herbarium mixed with other mosses 

 labelled as from Breemar. In addition to this uncertainty there is considerable doubt 

 whether D. Sauteri is anything more than a var. of D. longifolium ; the only important 

 differences being the more sparing denticulation and the considerably narrower nerve, 

 •J width of base ; several observers have found, however, that the former character is 

 not constant, and the Marchese Bottini states that he has found both plants growing 

 together, with many intermediate forms as regards even the width of nerve. I have 

 hardly felt justified, therefore, in retaining it as a species, whether or not it is actually 

 a British plant. 



Tribe J. Leucobryes. 



27. LEUOOBRYUM Hampe. 



Mosses of a peculiar habit, growing in dense white or 

 glaucous tufts, with close tumid foliation. Leaves composed 

 entirely of the nerve with the exception of a few rows on each 

 side (principally near the base) of very thin hyaline cells ; nerve 

 of two or more layers of large rectangular hyaline cells, their 

 internal walls perforated with large circular pores, with a 

 central layer of narrow chlorophyllose cells. Calyptra, capsule 

 and peristome dicranoid. 



The species of this genus are for the most part tropical, and 

 bear some superficial resemblance to Sphagnum in their colour 

 and their hygroscopic properties ; they are, however, intimately 

 allied to the Dicranacea?, and between them and species of 

 Dicranum such as D. longifolium and D. albicans, or, as far as 

 the leaves are concerned, C. fragilis in Campylopus, there is 

 practically no difference in structure of any real importance except 

 the pores in the cell-walls of the nerve. 



{Tall ; leaves 2-4 lines long ; capsule arcuate, strumose j . glaucum 

 Short ; leaves 1-2 lines long, thin ; capsule almost erect, hardly strumose 



'*- albidum 



1. Leucobryum glaucum Schp. (Tab. XIX. H.). 



In very dense soft tufts or patches, 2-8 inches high ; pale 

 glaucous green above, whitish below. Stems dichotomously 

 forked, robust, without radicles, very fragile. Leaves crowded, 

 erecto-patent or slightly secund, appressed when dry, entire, 

 tubular from the incurved margins, oblong-lanceolate or lanceolate 

 from an oval base, contracted at the insertion ; formed almost 



