Or WESTERN' PENNSYLVANIA. 25 



elliptic; branch-leaves squarrose in their apical half. 



5. S. compactum. 



m. Hyaline cells of stem-leaves fibrillose; chlorophyllose cells of 

 branch-leaves free on both surfaces; branch-leaves usually sub- 

 secund. n. (Subsecundtf . 



n. Cuticular sheath of stem 2-3-stratose. 



o. 



n. Cuticular sheath of stem 1-stratose. p. 

 o. Stem-leaves small, not over 1 mm. long, fibrillose only towards 



apex; branch-leaves secund. 15. S-. laricinum. 



o. Stem-leaves large, 1.5-2.0 mm. long, fibrillose to base or nearly 

 so; branch-leaves not secund. 16. S. platyphyllum. 



p. Stein-leaves with hyaline border strongly widened below, 



fibrils none or only in upper cells. 18. S. subsccnnJttin. 

 p. Stem-leaves with uniformly hyaline border, fibrils more 



numerous. q. 



q. Stem-leaves strongly auriculate. large. 1.5-2.0 mm. long, fibrillose 

 ''n upper two-thirds, at least, and at the base. 



17. S. grai'etii. 



q. Stem-leaves non-auriculate or but slightly auriculate. usually of 

 medium size, fibrillose in about upper two-thirds. 



r. 

 r. Stem-leaves about 1-1.5 mm. long, with septate hyaline cells 



and fibrillose in upper half. 19. S. inundatitm. 



r. Stem-leaves about 1.3-1.5 (-2) mm. long, very little septate, 

 fibrillose in upper two-thirds or to middle. 



20. S. pungens. 



s. Branch-leaves about 1-2 mm. long, strongly undulate and with 

 recurved tips when dry: dorsal pores of upper hyaline cells re- 

 stricted to cell-angles. 8. 5. recurvum. 

 s. Branch-leaves \vhen dry weakly undulate, scarcely recurved, about 

 1 mm. long, the upper hyaline cells with pores both in the cell- 

 angles and along the sides. 9. S. parvifolium. 



1. Sphagnum imbricatum (Hornschuch) Rtiss-\v. 



(S. anstini Sullivant). 



(Plate I) 



This species occurs in bog's and wet moors in Europe and 

 Asia and in Xorth America from Labrador to Alaska and south 

 to Louisiana. In our region it is represented by the following 

 variety. The typical form, as compared with the following 

 variety, has usually more yellowish or brownish denser tufts 

 with the shorter comal branches more erect and the divergent 

 branches more densely-leaved and more ascending; while the 

 hyaline cells of the stem-leaves are only sparsely comb-fibril- 

 lose on the inside face of the lateral walls ; otherwise the char- 

 acters of variety and species are identical : 



a. Sphagnum imbricatum variety sublaeve Warnstorf. 



(S. anstini var. glaiicnin f. squarrosulum Roell). 



Rather densely cespitose, large, usually more or less 



glaucous-green, grayish or yellowish below; stems rather 



stout, with us about 4-8 cm. long, the wood-cylinder greenish 



or yellowish and surrounded by a cuticular sheath of usually 



