Gyrothyra, a new Genus of Hepaticae. 



By Marshall A. Howe. 

 (Plates 302, 303.) 



GYROTHYRA. 



Stem creeping, foliose, subsimple or somewhat sparingly branch- 

 ing, radiculose. Leaves succubous, entire, alternate ; underleaves 

 present, free, bifid, segments narrowly lanceolate or subulate; 

 walls of the leaf-cells with triangular thickenings at the angles. 

 Antheridia short-stalked, in the axils of smaller saccate leaves, form- 

 ing short median or, at first, terminal spikes. Involucral leaves 

 2-4 pairs (commonly 3 pairs). Perianth terminal, confluent for 

 half its length or more with the bases of the involucral leaves, the 

 greater part of the calyptra, and the tissues of the stem, to form a 

 thick- walled tube (perigynium) , with a small bulbous or saccate base; 

 perigynium erect or ascending, making, at maturity, nearly a right 

 angle with the stem. Capsule cylindrical, long-exserted, dehiscing 

 spirally by four very long and slender valves ; capsule-valves 

 of two layers of cells, whose walls are wholly destitute of spiral, 

 semiannular, or other local thickenings. Elaters free, bispiral, 



