OF WESTERN PENNSYLVANIA 237 



smooth, ecostate; foliate leaves pluriseriate, dense, spreading, 

 rarely secund, drying appressed to imbricate, symmetric, apex 

 sometimes one-sided, mostly acuminate, mostly concave, often 

 with two short folds at base, unistratose, mostly papillose; 

 costa mostly simple and strong, rarely short, double, delicate, 

 or forked ; cells richly chlorophyllose, mostly parenchymatous, 

 small, often oblong to linear, in the jniddle of the base, or up 

 to the middle of the leaf; branch-leaves' usually shorter and 

 narrower than the stem-leaves; perichaetial leaves delicate, 

 hyaline, much- elongate, ecostate or weakly costate: seta 

 straight and long; capsule erect and symmetric to cernuous 

 and arcuate, non-plicate; annulus usually present; peristome 

 double, the teeth mostly basally confluent, prominently articu- 

 late and trabeculate or dorsally uniformly papillose, with weak 

 ventral plates, whitish to red or brownish, often quite red at 

 the insertion ; inner peristome carinate, with basal membrane, 

 segments, and, rarely, with cilia ; lid conic or convex-conic and 

 rostrate ; calyptra cucullate ; spores mostly small. 



A large family, mostly in temperate and tropic regions, 

 occurring mainly on trees and rocks; 23 genera; 15 genera in 

 our region . 



Key to the Genera. 



a. Archegonial clusters borne on the branches: primary stems 

 stoloniform with minute leaves; costa simple; capsule erect, sym- 

 metric; segments filiform or rudimentary. 



b. 

 a. Archegonial flowers on the stem; stem not stoloniform. 



c. 

 b. Very slender; costa not reaching above the middle of the leaf: 



peristome-segments none. 3. Haplohymenium. 



b. More or less robust; costa ending in or just below apex; peri- 

 stome-segments filiform. 4. Anom-odon. 

 c. Costa short, simple, forked, double, or none. 



d. 

 <.. Costa simple (except Pseud o-Leskiella), elongate, ending a little below 

 the apex, or excurrent. e. 



d. Stem creeping, densely simply pinnate, costa short, simple or 

 forked; teeth non-bordered, non-trabeculate. 



1. Thelia. 



d. Stem ascending to erect, irregularly bushy-branched; costa in- 

 distinct or none; teeth bordered, trabeculate. 



2. Myurella. 



e. Leaves of stem and branches alike; stem creeping with ascending 



or erect, short, blunt branches. f. 



e. Stem and branch-leaves unlike; stem 1-3-pinnate, often quite fern- 

 like in general form. h. 

 f. Teeth without distinct lamellae; segments filiform. 



7. Leskeella. 

 ■f. Teeth distinctly lamellate; segments narrowly linear or none. 



g. 

 g. Teeth with well-developed lamellcc; segments narrowly linear. 



6. Leskea. 

 g. Teeth with distinct but low lamellae; segments none. 



5. Lindbergia. 



