OF WESTERN PENNSYLVANIA 271 



teeth, slightly carinately split, the basal membrane about two- 

 fifths as high ; cilia usually 3, pale, papillose, some of them as 

 long as the teeth, nodose; annulus rather large, two-seriate; 

 upper exothecial cells small, rounded-hexagonal or quadrate, 

 below becoming elongate-hexagonal or oblong-rectangular; 

 spores in late spring or early summer, somewhat incrassate, 

 castaneous, minutely roughened, about .015-018 mm. 



On moist earth in swampy or marshy places; Europe, Asia, 

 and probably throughout temperate North America. Fairly com- 

 mon in our region but in its smaller sizes difficult to satisfactorily 

 distinguish from A. jiiratzkanuin. 



Allegheny : On wet woods-humus, Guyasuta Hollow, 



October 12, and October 25, 1908. O. E. 



J.; Kennywood, May 3, 1902, Moon 



Township, May 18, 1902. J. A. S. 



Center : On wet, clayey soil in Barrens near Scotia, 



July 14, 1909. O. E. J. 

 Crawford : Linesville, Pymatuning Swamp, Tune 12, 



1907. O. E. J. 

 Fayette : Ohio Pyle, June 11, 1908. O. E. J. 



Lawrence : New Castle, 1906. Miss Susan Gageby. 



McKean : West Branch Swamp, November 15, 1899. 



D. A. B. 

 ^^'ashington : On damp roots of black walnut, Hanlin, 



May 21, 1908. O. E. J. 

 \V^estmoreland : On wet rocks at edge of stream. Hillside, 

 Alay 19, 1906, and Garrett Farm, near 

 Trafiford, August 21, 1910. O. E. J. 



7. Amblystegium riparium [Linnaeus] Bryologia Europsea. 



(Hypnum riparium Linnaeus ; H. laxifoUum Bridel ; Stereodon 

 riparium Mitten). ■ 



(Plate XXXVHI) 



Loosely cespitose, yellowish-green, the flat tufts soft: 

 stems creeping, sub-pinnate, the branches usually 2 or 3 cm. 

 long, spreading to horizontal, the stems sometimes floating and 

 reaching a length of 8 or 10 cm.; stem-leaves 2-4 mm. long, 

 rather widely spreading or almost squarrose both wet and dry, 

 often somewhat complanate, at tips of branches more or less 

 secund, widely lance-ovate to oblong-lanceolate, gradually 

 tapering to a fine, flat, non-channeled acumination, shortly de- 

 current, rounded at base, non-auriculate, somewhat excavate ; 

 branch-leaves similar but smaller, all leaves entire and plane- 

 margined ; costa fairly strong, reaching from one-half to three- 

 fourths the length of the leaf; median leaf-cells linear-rhom- 

 boid, prosenchymatous, usually 8-12(-15) :1, thin-walled, 

 chlorophyllose, towards the base lax and sub-rectangular, at 



