440 



POTTIACEAE. 



5. HYMENOSTYLIUM Brid. 

 Plants in dense crowded tufts; stems tall, slender and branching; leaves 

 crowded small, lanceolate-acuminate; vein single, ending below the apex; cells 

 smooth or papillose; pedicel erect, elongate; capsule erect, ovoid and shining; 

 peristome lacking; lid with a long beak; calyptra cucullate. [Greek, referring 

 to the membrane covering the mouth of capsule.] A genus of 17 species 

 widely distributed on limestone rocks, mostly in tem- 

 perate regions. Type species : Eymenostylium xanthro- 

 carpum (Hook.) Brid. 



1. Hymenostylium curvirostre (Ehrh.) Lindb. 

 Curved-beaked Hymenostylium. (Fig. 482.) Plants 

 in pale green calcareous cushions; stems up to 1' high, 

 slender and leafy branches short ; leaves crowded, re- 

 curved and twisted when dry, spreading when moist, 

 lanceolate-acuminate, short; vein stout, smooth, ending 

 below the apex; margins entire, often slightly re- 

 curved at base; basal cells rectangular, clearer and 

 larger than the papillose upper cells. Pedicel terminal, 

 becoming lateral by innovations, more or less per- 

 sistent; capsules ovoid-pyriform, erect, with a long- 

 beaked lid which is more or less persistent; annulus 

 narrow; peristome none, mouth closed by a mem- 

 brane; spores large, maturing in summer. [Pottia 

 curvirostris Ehrh.] 



Thus far only found sterile under dripping rocks in caves forming lime-encrusted 

 cushions. Widely distributed in temperate regions of North America and Europe, 

 always on calcareous rocks. 



6. TOBTULA Hedw. 



Plants of various sizes, sometimes large and stout; usually 



growing on the ground or on rocks in dense cushions; stems 



usually simple, rarely branched; with the leaves crowded at the 



top of the stem, usually spreading when dry, or twisted, mostly 



broader above the middle, usually entire, with a single vein, 



sometimes excurrent into an awn, with the basal cells long and 



clear and the upper small and dense, sometimes papillose. 



Pedicel erect, elongate; capsule erect, cylindric; lid usually 



long-beaked; calyptra cucullate; peristome single, usually 



twisted; teeth 16 or 32; slender, papillose; spores small. [Latin, 



with reference to the twisted peristome.] A large genus of 



186 species widely distributed in all parts of the world. Type 



species: Bryum miirale L. 



1. Tortula agraria Sw. Common Tortula. (Fig. 483.) 

 Plants up to 9" high, almost stemless, forming a rosette of 

 basal leaves, not much curled or twisted when dry; widest 

 above the middle, base oblong with clear, long cells; apex 

 acute, cells square, smooth, vein stout ending in a mucronate 

 point. Pedicel erect; capsule cylindric, ribbed when dry; 

 annulus present; lid long-conic-beaked, red at base; peristome 

 red, papillose twisted ; teeth 16, long and slender, bifid or trifid 

 with a short basal membrane ; calyptra cucullate ; spores 

 smooth, small, maturing in spring. [Barhula agraria Hedw.] 



Common on" limestone from Florida and Texas to Mexico and 

 from the Bahamas through the West Indies to South America. 



