194 American Midland Naturalist Monograph No. 6 



secondary stems stoloniferous; paraphyllia mostly present; leaves rarely uni- 

 form, usually differentiated into basal and foliate leaves, the latter again into 

 stem-leaves and branch-leaves; basal leaves distant, small, delicate, pale, 

 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 middle 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 

 plicate; annulus usually present; peristome double, the teeth mostly basally 

 straight and long; capsule erect and symmetric to cernuous and arcuate, non- 

 confluent, prominently articulate and trabeculate or dorsally uniformly papil- 

 lose, 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; peristome often degenerate in the species with erect cap- 

 sules; lid conic or convex-conic and rostrate; calyptra cucullate; spores mostly 

 small. 



As here treated this is a large family of about 30 genera sometimes, as by 

 Brotherus, separated into three families: Leskeaceae, Theliaceae, and 

 Thuidiaceae. 



Mostly in temperate and tropic regions, mainly on trees and rocks. 

 Eleven genera occur in our general region. 



Key to the Genera 



A. Archegonial clusters borne on the branches: primary stems stoloniform with minute 

 leaves; costa simple; capsule erect, symmetric; segments filiform or rudimentary; 



cilia usually none 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; peristome-segments fili- 

 form 4. Anomodon 



C. Costa short, simple, forked, double, or none, never reaching much above middle of 



leaf D 



C. Costs simple (except Pseiido-Leskeella) , elongate, ending a little below the af>ex, 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 indistinct 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 



I . Teeth distinctly lamellate; segments narrowly linear or none G 



G. Teeth with well-developed lamellae; segments narrowly linear 6. Leskea 



G. Teeth with distinct but low lamellae; segments none 5. Ltndbergia 



H. Cilia 3, smooth; cells of stem-leaves elongate-hexagonal to almost linear; stem and 



branch-leaves similar; paraphyllia felted along stem and leaf-base ....11. Helodium 



