OF WESTERN PENNSYLVANIA. 11 



ANALYTICAL KEY TO THE 

 GENERA OF MOSSES OF WESTERN PENNSYLVANIA 



Order l.—SPHAGNALBS 

 Whitish mosses with fasciculate branches, 

 mostly bog plants; leaf-cells of two kinds, — 

 large hyaline ones separated by narrow chloro- 

 phyllose ones; ecostate; operculate but with 

 no peristome. Sphagnum, p. 23 



Order ll.—ANDRBAEALBS 

 Dark colored or blackish alpine or subalpine 

 plants growing in cushions on granitic or slaty 

 rocks; either costate or ecostate; leaf-cells 

 small and quite opaque; capsule dehiscing by 

 four longitudinal slits, the valves remaining 

 united at the apex. Andreaea, p. 46 



Order III.— BRY ALES 

 Leaves various but not sphagnoid, costate or 

 ecostate; capsule dehiscing irregularly or, more 

 often, by a deciduous operculum, often fur- 

 nished with a peristome, never four-valved as 



in Andreaea, plants largely green .1. 



I. Sporophyte borne at the apex of the main 

 stem, sometimes appearing lateral by the 



growth of a branch A. Acrocarpi, p. 48 



\. Sporophyte borne at the apex of a short 



lateral branch B. Pleurocarpi, see p. 16 



A. ACROCARPI 



1. Capsule non-operculate 2. 



1. Capsule operculate 10. 



2. Green protonema persistent; plants 



fruiting in autumn Bphemerum, p. 127 



2. Green protonema not persistent, 



plants fruiting mainly in spring. 3. 



3. Spores few, about 16 to 20, smooth, about 



0.2 mm. in diameter Archidium, p. 48 



3. Spores numerous, rarely exceeding 0.05 



mm. in diameter 4. 



4. Leaf-margins plane or involute. 5. 

 4. Leaf-margins more or less revo- 



lute 9. 



5. Capsules pyriform, with a distinct neck 6. 



5. Capsules globose to ovoid 7. 



6. Green protonema occasionally abun- 

 dant; neck none; capsule acute Sporledera, p. 49 



6. Green protonema sparse; usually 

 none; neck more or less well de- 

 veloped; capsule rostrate Bruchia, p. 50 



7. Leaves crisped when dry, strongly pa- 

 pillose on both sides; operculum rudi- 

 mentary but persistent Astomum, p. 89 



7. Leaves not crisped when dry, smooth . 8. 

 8. Calyptra cucullate; leaves linear- 

 lanceolate to lanceolate-subulate . . . Plcnridium, p. 52 

 8. Calyptra campanulate; leaves lan- 

 ceolate-ovate to lanceolate-obovate, 

 dentate or serrate Physcomitrella, p. J30 



