OF WESTERN PENNSYLVANIA 199 



brown, apophysis distinct; cells of exothecium more or less 

 hexagonal, the central pore round to oblong, often one-third 

 the diameter of the whole cell; peristome about 0.2 mm. high, 

 teeth rather slender ; calyptra yellowish-brown, covering the 

 capsule ; operculum flattened, the rostrum about 0.5 mm. long. 

 Evidently mature in midsummer. 



From the Northern States to the Arctic regions ; south 

 ern South America ; northern Europe and Asia. In bogs or 

 boggy woods. Rare in our region. 



Crawford : In small Cassandra bog near Linesville, May 



28, 1908. O. E. J. (Figured). 



Washington : Hanlin, in tuft of Leucobryntm. May 21, 



1908. O. E. J. 



5. Polytrichum commune Linnaeus, Hedwig. 



(Plate XXIX) 



Large, erect, 10-20 cm. high, loosely cespitose in large 

 masses, rather dark olive green : stems simple, flexuous, woody, 

 slightly or not tomentose at base, chestnut-brown, rather 

 densely foliate above ; lower leaves small, linear, becoming 

 gradually larger above up to about 15 mm. long, the limb 

 linear-lanceolate from an oblong sheathing base, when moist 

 spreading or recurved, when dry appressed-erect, serrate to 

 the sheathing base, the apex linear, serrate, pellucid; areola- 

 tion at base of sheath parenchymatous, rectangular, above 

 becoming linear-prosenchymatous, abruptly grading at base of 

 limb into rounded incrassate cells about .010-.015 mm. in 

 diameter, towards apex becoming elliptic with the longest 

 diameter transverse, all pellucid to more or less opaque ; 

 lamellae 40-60, 5-7 cells high, the terminal cell broader and 

 retuse to bi-cuspidate at apex, the lamellae extending almost 

 to the base of limb ; perichaetial bracts w r ith a longer sheathing 

 portion and few or no lamellae ; antheridial flowers conspicu- 

 ous, cup-shaped, the broadly obovate shortly acuminate bracts 

 which form the cup being about 4 mm. long, the costa broad 

 and weak below but stronger and bearing numerous lamellae 

 in the upper half; the successive annual growths of the male 

 plant taking place from the center of the antheridial flower 

 of the preceding season: seta wiry, flexuous, 6-10 cm. long, 

 lustrous, chestnut to light golden-brown; capsule erect, but 

 later inclined, and, when old and empty, cernuous, light to 

 deep chestnut-brown, more or less cubical or shortly rectan- 

 gular, apophysis discoid, distinct ; capsule-urn about 3-5 mm. 

 long ; operculum low-conic, the beak about 1 mm. long ; peris- 

 tome-teeth about 0.25 mm. high, more or less reddish-pellucid; 

 exothecial cells hexagonal, the outer face convex and with a 

 rounded to elliptic pore; spores round, smooth, about .008- 



