58 MUSCI 



b. Leaves with a hyaline margin. 



I. Margin faint. Capsule irregular with a distinct gizzard. 



(i) 15. Dicranol6ma 



II. Margin distinct. Capsule erect, regular. 



(Plate 6, 1).) (4) 16. Leucol6ma 



Fam. 7. Pot t i aceae. 



A. Leaves mostly narrow ; cells of lamina small. 



a. Lid not distinct. 



(Plate 6, G.) (1) 17. Astomum 



b. Lid distinct, deciduous. 



I. Peristome absent. 



1. Orifice of capsule closed with a membrane after the dropping of 



the lid. 



18. Hymenostomum 



2. Orifice of capsule open when lid falls oft*. 



(1) 19. Hymenostylium 



II. Peristome present. 



1. Outer layer of peristome thicker than the inner one, with 



conspicuous transverse ridges. 



(1) 20. Weisia 



2. Both layers of peristome similar, without transverse ridges. 



x heaves triseriate. 



(2) 21. Triquetrella 

 x x Leaves pluriseriatc. 



o Leaves with flat or slightly recurved margins. 



§ Teeth of peristome or its divisions erect and straight. 



(1) 22. Trichostomum 



§§ Teeth of peristome or its divisions spirally twisted to the left. 



(6) 23. Tortella 



00 Margin of leaves recurved distinctly, at least at tbe base. 

 \ Teeth of peristome erect or slightly inclined to tbe right. 



(1) 24. Didymodon 



SS Teeth of peristome spirally twisted to the left. 



(8) 25. Barbula 



B. Leaves broad. Cells of lamina large. 

 a. I .id not distinct. 



I. Capsule globular, without a mucro. 



(1) i(>. Acaulon 



II. Capsule globular or ovate, mucronate. 



(2) 27. Phascum 



