OF WESTERN PENNSYLVANIA 133 



apiculate ; calyptra long' and erect-rostrate, mitrate, lobed to 

 the base of the beak, covering one-half or less of the capsule. 



A cosmopolitan genus of about 75 species; 17 species in 

 Xorth America, at least 2 species in our range. 



Key to the Speeies. 



a. Seta very short: capsule immersed, wide-mouthed; calyptra small. 



1. P. immersion. 



a. Seta longer; capsule exserted. not wide-mouthed: calyptra larger. 



2. P. turbinatitin. 



1. Physcomitrium immersurn Sullivant. 



(Gyinnostoiiiiiiii iitittiersuiu Sullivant ). 



( Plate XVI) 



Plants small, erect, gregarious, light green, simple or 

 branching, 3-8 mm. high; leaves 1.5-3.5 mm. long, obovate 

 to oblanceolate. serrate above the middle, spreading to ascend- 

 ing; costa strong, ending a little below the apex; leaf-cells 

 parenchymatous, rather large and thin-walled, the basal rec- 

 tangular, about 2-5 :1, the upper irregularly oblong, the 

 marginal narrower and in the alar region a few much shorter: 

 capsule immersed, globose to pyriform-globose, 0.6-0.9 mm. 

 in diameter, apiculate-rostrate, about the upper two-fifths con- 

 stituting the operculum, yellow-brown when ripe ; seta con- 

 siderably shorter than capsule and stout : exothecial cells ir- 

 regularly quadrate to hexagonal, somewhat incrassate, the 

 annulus consisting of one to three rows of much smaller, 

 orange-pellucid, to brown-pellucid cells, the cells of the wall 

 usually laterally elongated for one or two rows above and be- 

 low the annulus ; calyptra mitrate, the basal margin 4-5- 

 lobed, covering about one-half of the operculum ; spores dense- 

 ly papillose, orange to brownish-pellucid, globose, in our speci- 

 mens about .035 mm. in diameter, mature in autumn. 



Usually on clayey or sandy Mood-plains where submerged 

 in time of freshets. Quebec to Colorado and Delaware but 

 not commonly collected, probably on account of its ^mall size 

 and special habitat. 



Beaver : Clay bank of Little Heaver Creek. Xew 



dafilee, September 10, 1906. O. E. J. ; 

 Lank of Ohio River, Smith's Ferry, Oc- 

 tober 1, 1910. O. E. J. ( Figured). 



McKean : East Branch, Bradford. June 15. 1895. D. 



\. B. 



2. Physcomitrium turbinatum (Richardson) C. Mueller. 

 (Phascum strangidatiim Kindberg; Phascnin hookcri Macoun'). 



( Plate XVI) 



Gregarious, often densely so, light green: stems 3-5 mm. 

 high, erect, usualh' simple; leaves 3-5 mm. long, lance-ob- 



