TRICIIOSTOMEI. 259 



c. Leaves rigid ; nerve clothed with jointed threads (Tortula). 



22. T. aloides, Wils. ; dioicous ; stem short; leaves spread- 

 ing, linear-lanceolate, acute, strongly nerved; margin in- 

 curved ; sporangium cylindrical, oblique ; fruitstalk curved 

 above ; ring fragmentary ; lid rostrate from a conical base ; 

 teeth in pairs, scarcely twisted. — Hook, fy Wils. t. xlii. ; Eng. 

 Bot. t. 180, 2759. ; (Moug. fy Nest. n. 717.) 



On clay banks. Bearing fruit in winter. 



Extremely short. Leaves more rigid with a stronger nerve ; 

 margin strongly incurved ; basal membrane rather broad ; 

 teeth divaricated when dry, pallid ; spores larger than in the 

 two following species; nerve, which is prominent below, 

 though not above, and part of the disk, concealed by a 

 mass of jointed threads analogous to the plates in Polytri- 

 chum. 



23. T. ambigua, Wils. ; dioicous ; stem short ; leaves 

 spreading, ligulato-lanceolate from an ovate base ; rather ob- 

 tuse, concave, incurved, and cucullate above; margin in- 

 curved; sporangium cylindrical, erect ; teeth slightly twisted. 

 — Hook. §• Wils. t. xlii. 



On walls and banks. Common on the caps of the oolitic 

 walls in Northamptonshire. Bearing fruit in winter. 



Stem very short ; leaves stellate ; teeth incurved when dry, 

 red, filiform at the base. Distinguished from the last by its 

 erect sporangium, and from the following by its cylindrical 

 sporangium, besides other points. 



24. T. rigida, Wils. ; dioicous; stems -short; leaves spread- 

 ing, oblong, obtuse; margin membranaceous, inflexed; spo- 

 rangium elliptico- oblong, straight, erect; ring distinct; lid ob- 

 liquely rostrate; peristome rather long, much contorted. — 

 —Hook. $ Wils. t. xxxii. ; Grev. Sc. Crypt. Fl. t. 331. ; (Moug. 

 $■ Nest. n. 613.) 



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