OF WESTERN PENNSYLVANIA 311 



McKean : Bennett Brook, May 3, 1893, Langmade 



Hollow, May 5, 1894, Marilla Brook, 

 Bradford, June 30, 1895. D. A. B. 



Fayette : Ten different collections from Ohio Pyle, 



O. E. J., G. K. J. and J. A. S. 



Mercer : Half-Moon Swamp, June 12, 1906. 



O. E. J. 



Somerset : Ursina, May 12, 1905. O. E. J. 



AA'ashington : Three miles southwest of Library, April 

 29, 1906. O. E. J. 



Westmoreland: "Shades," near Blackburn, June 13, 1908. 

 O. E. J.; and same locality March 25, 

 1910. O. E. J. and G. K. J. 



6. Stereodon arcuatus (Lindberg) Lindberg. 

 {Hypnum arcuatttm Lindberg ; H. lindbergii Mitten ; H. patientiae 

 Lindberg) . 



(Plate XLVI) 



Robust, widely cespitose in yellowish-green mats, usual- 

 ly more or less regularly pinnate, lustrous at least on the 

 younger parts : stems prostrate, usually sparsely branched ; 

 stem-leaves about 1.6-2.2 mm. long, complanately falcate- 

 secund, lustrous, ovate-oblong, decurrent, the margins plane 

 and entire or sub-denticulate at the apex, the leaves rather 

 shortly and broadly acuminate, the tip flat and widely acute to 

 somewhat obtuse, the decurrent auricles are made up of large, 

 oblong, inflated, thin-walled, and hyaline cells bordered above 

 by about two series of smaller, quadrate, usually brownish- 

 pellucid, thicker-walled cells, these latter grading quickly into 

 linear-vermicular median cells about 12-20:1, the apical cells 

 oblong-rectangular or obliquely more or less rhomboidal ; costa 

 very short and double or none; branch-leaves similar; peri- 

 chaetial leaves sheathing, the inner lanceolate to lance-linear, 

 up to 6 or 7 mm. long, plicate, entire, acuminate ; seta about 

 2.5-3 cm. long, dextrorse, lustrous, castaneous; capsule about 

 2-2.5 mm. long, about 4-5 :1, oblong-cylindric, erect at base 

 but arcuate so that the lid usually points more or less hori- 

 zontally, when dry plicate but scarcely narrowed, below the 

 mouth; annulus large, revoluble; lid conic, apiculate, scarcely 

 longer than wide; peristome hypnoid, the teeth lance-linear, 

 dorsally cross-striolate, yellowish-pellucid below, hyaline and 

 papillose above, the divisural and dorsal lamellae^ prominent, 

 the trabeculae strong and numerous; segments rising from a 

 basal membrane about two-fifths the height of the teeth, the 

 segments about as long as teeth, narrow, somewhat carinately 

 split ; cilia 1-3, shorter, nodose, hyaline-papillose, often joined 

 together above; spores smoothish, yellowish, moderately in- 

 crassate, about .014-.018 mm., mature in spring. 



