37 
Analytic Keys to the Species of Mosses. 
■» i 
Leaves mostly blunt-pointed, cells rectangular, spores 
24-82 n .S. tristicha, 4, 
Seta arcuate when moist ....... S. recurvata, 3. 
PGTTIA, p. 100. 
I. Peristome 0 or rudimentary. 
Costa with 2-4 lamellae above ..... P. cavifolia, 1. 
Costa not lamellate. 
Leaf-margins more or less re volute. 
Lid conic obtuse, spores echinate .... P. minutula, 2. 
Lid rostellate, spores papillose. 
Calyptra smooth . . . , . . . P. truncata, 3. 
Calyptra scabrous.P. Wilsoni, 4. 
Leaf-margins plane or involute. 
Lid abruptly rostrate, leaves sharply serrate above . P. Heimii, 5. 
Lid conic, leaves distantly denticulate above . . P. riparia, 6. 
Lid conic-subulate, leaves slightly crenulate above . P. Barb ill a, 7. 
II. Peristome distinct. 
Leaves oblong-lanceolate, margins revolute . . . P. Starkeana, 8. 
Leaves rounded or round-spatutate, margins plane . P. latifolia, 9. 
DIDYMODON, p. 104. 
Leaf cells throughout quadratic.I), lurid US, 2. 
Leaf cells below rectangular. 
Leaf base reddish, margins above revolute D. rubcllus, 1. 
Leaf base hyaline, margins plane . . . . D. cylindrieus, 8. 
LEPTOTRICHTJM, p. 105. 
Dioicous. 
Leaves slightly twisted. 
Stem leaves spreading, perichaetial leaves hardly 
sheathing.L. tortile, 1. 
Stem leaves imbricate, perichaetial leaves long sheath¬ 
ing .L. vaginalis, 2. 
Leaves not twisted. 
Plants short (1-2 cm.), not radiculose . . . L. Iiomomallum, 8, 
Plants long (to 10 cm.) densely radiculose . . L. flexicaule, 4. 
