180 TORTULACE^. 



6. Tortula aloides De Not. (Trichostomum aloides Koch - r 

 Barbula aloides Fiirnr., Schp. Syn.,) (Tab. XXVII. D.). 

 Resembling T. ambigua, but with the leaves distinctly 

 longer, narrowed above and acute, not cucullate at apex, 

 mucronate with the excurrent nerve. Seta bent just below the 

 neck of the capsule, which is therefore inclined. Calyptra. 

 reaching a little below the lid ; capsule cylindric, slightly curved 

 or swollen on one side ; peristome teeth once twisted, convergent 

 above when dry ; spores larger, about 25 ju. in diameter. 

 Annulus narrow, persistent. Dioicous. 



Hab. Calcareous banks and wall tops. Not common. Fr. winter. 



Easily known by the narrowed, acute leaves, and the inclined capsule. The 

 peristome teeth show considerable variation both in length and direction. 



C. DESMATODON. 



7. Tortula subereeta Drumm. (Desmatodon obliquus B. & S. r 



Schp. Syn. et plur. auct.) (Tab. XXVII. E.). 



Short, tufted or gregarious, dull or yellowish green. Leaves 

 erecto-patent, slightly crisped when dry, thin, concave, ovate- 

 oblong or ovate-lanceolate, acute or acuminate ; margin revolute 

 to near apex, eritire or faintly denticulate above ; nerve excurrent 

 in a rather long yellowish hair ; cells above hexagonal, obscure, 

 papillose, one or more rows at margin more pellucid, forming a 

 paler border. Seta slender, capsule oblique, sub-cylindric, slightly 

 curved or straight ; basal membrane rather long, teeth fragile, 

 oblique, but hardly spirally twisted. Spores rather large, strongly 

 papillose. Autoicous. 



Hab. Alpine rocks. Very rare. Scotland (v. Braithw., Br. M. Fl., Vol. I., 

 p. 277). Fr. late summer. 



Nearly allied to T. systylia and other species of the genus Desmatodon Brid., 

 it differs in the acuminate, aristate leaves, usually faintly denticulate above, from that 

 and all the allied species. 



T. systylia (Desmatodon systylius B. & S. ) exists in some old herbaria labelled as- 

 Pottia cavifolia var. pihfera, and purporting to have been gathered by Dickson near 

 Aberfeldy. It is an alpine plant, found in Norway and Central Europe, and is hardly 

 likely to have been found in the locality named. It differs from the present species in 

 the erect capsule and entire leaves with plane margins, from T. atrovirens in the 

 longly excurrent nerve and plane borders. 



8. Tortula atrovirens Lindb. (Grimmia atrovirens Sm. ; 

 Barbula atrovirens Schp., Syn. ; Desmatodon nervosus B. & S., 



plur. auct.) (Tab. XXVII. F.). 



Densely gregarious or tufted, short, dark green. Leaves 

 spreading, spirally twisted and imbricated when dry, oval-oblong 



