TRICHOSTOMUM. 221 



the leaves very closely and neatly circinate-incurved so that the points are hidden, 

 while in Tr. tortuosum and frequently in Tr. Jlavovirens they are more or less 

 spirally twisted upon themselves, in corkscrew fashion, less closely imbricated and 

 with the points more or less projecting and visible. The nerve also is much more 

 shining and glossy than it is (with at any rate very rare exceptions) in either, and the 

 leaves more fragile. The var. fragilifolium of Tr. tortuosum perhaps most nearly 

 resembles it, but is usually more loosely tufted and the leaves less closely imbricated 

 when dry, and less shining. Tr. inclinatum is known by the paler colour, flat 

 extended tufts, less fragile and less shining leaves. Tr. fragile is quite distinct in 

 the leaves hardly curled when dry. Tr. mutabile is sometimes much like it in appear- 

 ance, but the basal areolation is quite different. 



In the above remarks, as in the description, I have referred to the plant in its 

 ordinary form, as, I believe, it is always found in this country. 



8. Trichostomum tortuosum Dixon (Bryum tortuosum L. ; 



Mollia tortuosa Schrank, Braithw. Br. M. Fl. ; Barbula 



tortuosa W. & M., Schp. Syn.) (Tab. XXXII. C). 



In tall rounded tufts, small or extended, 1-4. inches high, pale 

 or yellowish green above, yellowish brown below. Stems robust, 

 radiculose below ; leaves crowded, fragile, very long, (2-j lines), 

 spreading and flexuose, when dry strongly curled or spirally 

 contorted on themselves , the nerve pale and shining at back ; 

 from a pale whitish base longly linear, tapering to a slender 

 subula, undulate, margin flat at point ; nerve strong, pale, 

 excurrent in a fine entire or slightly denticulate point ; cells at 

 base thin, rectangular, hyaline, reaching for some distance up the 

 leaf and extending obliquely very high at the margin, abruptly 

 becoming small, chlorophyllose, in all upper part rounded, rather 

 large for the genus, less obscure than in some of the previous 

 species, papillose, crenulate-papillose at margin. Seta long, red 

 below, pale above ; capsule shortly or longly cylindric, straight or 

 slightly curved, lid rostrate, nearly as long as the capsule or much 

 shorter ; peristome very slender, long, much twisted. 



Var. yS. dicranoideum (Mollia tortuosa var. dicranoidea Ferg. 

 MS., Braithw. Br. M. Fl.). Taller, compactly tufted, densely 

 radiculose nearly to apex ; leaves firm, rigid, subsecund, the 

 terminal ones collected into a cuspidate tuft. 



Var. y. fragilifolium (Barb, tortuosa var. fragilifolia 

 Juratz.). In short small tufts; leaves smaller, shorter, less 

 finely tapering, very fragile, nerve excurrent in a yellowish 

 point, very glossy and pale at back when dry ; leaves when dry 

 less strongly contorted, but more closely incumbent. 



Hab. Rocks and mountain slopes, principally in calcareous regions, frequent. 

 The var. 0, Scotland ( Fergusson) ; the var. 7 on exposed alpine rocks, walls, etc. ; 

 rare. 



