260 HANDBOOK OF BRITISH MOSSES. 



On walls, especially in calcareous districts; chalk pits, etc. 

 Bearing fruit in winter. 



Very like the last two, but distinct in the form of the spo- 

 rangium, which is half covered by the veil, which in those 

 species is much shorter. 



82. TBICHOSTOMUM, Br. Schimp. 



Sporangium erect or more rarely curved; veil cucullate, 

 smooth; peristome single, of thirty-two more or less perfect, 

 straight teeth, disposed in pairs, composed of a single series of 

 elongated cells, sometimes so united or perforated as to look 

 like sixteen, connected by a narrow basal membrane ; leaf- 

 cells punctiform above, minutely papillose, rectangular and 

 hyaline below. Perennial, terrestrial Mosses, with the habit of 

 Tortula. 



1. T. rigidulum, Smith; tufted; leaves spreading and re- 

 curved, elongato-lanceolate, keeled ; margin recurved ; nerve 

 subexcurrent ; sporangium subcylindrical ; ring narrow ; teeth 

 in pairs or free, sometimes connected by transverse bars. 

 Hook, ty Wils. t. xx.; Eng. Bot. t. 2178.; (Moug. Nest. n. 

 612.) 



On moist rocks or upon dry, exposed, calcareous walls. 

 Bearing fruit in autumn and winter. 



Loosely tufted. Stem straight, about an inch high, of a 

 brownish or dull green; leaf-cells distinct, punctiform; lid 

 obliquely rostrate. When growing on dry walls it is shorter, 

 the sporangium more elliptic, and the lid longer. 



2. T. tophaceum, Brid. ; stem branched, elongated ; leaves 

 spreading from an erect base, lanceolate, obtuse ; nerve ceasing 

 below the tip, keeled, concave; sporangium oblong, subcylin- 

 drical ; ring none ; lid obliquely rostrate ; teeth irregular, in 

 pairs. Hook. mis. t. xx. ; Eng. Bot. t. 1598, 1707,2295. 



