116 American Midland Naturalist Monograph No. 6 



A genus of tliree species, on damp soil. One in Cuba and the following 

 two in temperate North America: 



Key to the Species 



A. With strongly collenchymatous exothecial cells; capsule rather regularly dehiscing 



1. A. serratum 



A. Exothecial cells not collenchymatous, thin-walled; capsule not regularly dehiscing 



2. A. patens 



1. Aphanorhegma serratum (Hooker, f. and Wilson) Sullivant 



Plate XX 



Gregarious, light green: stems erect, simple or forking, 1-5 mm high, radicu- 

 lose at base; leaver* small and lance-oblong below, rapidly becoming larger up 

 to 3-5 mm long, narrowly lance-obovate above, the lower widely spreading and 

 flexuous, the inner erect-spreading, thin, slightly serrate above the middle, apex 

 acute to acuminate: costa medium, ending in or just below the apex; the 

 median basal cells thin-walled and more or less inflated, rectangular, the mar- 

 ginal narrower, a few quadrate at the base, becoming linear-rectangular above 

 the base, in the upper part of the leaf their tips extending as low serrations, 

 the median rhomboid to short rectangular with walls medium, the apical 

 longer and narrower: seta very short and stout; capsule brown when ripe, glo- 

 bose to depressed-globose, about 0.75 mm in diameter, smooth to apically 

 papillose, splitting in the middle along a line of one or two rows of small 

 more or less orange-pellucid cells, the upper half of the capsub (operculum) 

 apiculate-rostrate; exothecial cells of capsule quadrate, conspicuously collen- 

 chymatous; calyptra hyaline, conic-mitriform, 4-6-lobed, covering the upper 

 half of the operculum; spores globose, about .030 mm in diameter, orange- 

 pellucid or even darker, mature in autumn. 



On damp clayey soil in the northern and middle United States, in our 



region usually along streams where submerged during periods of high water. 



Now known from Allegheny, Butler, Clarion, Fayette, Greene, Potter, Washingon, 

 and Westmoreland counties. Specimen figured: Cheat Haven, Fayette Co., Sept. 6, 1910. 

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



2. Aphanorhegma patens (Hedwig) Lindberg 



(Physcomitrella patens [Hedw.] Bryologia Europaea; Phascum patens Hedwig) 

 Gregarious, pale green: stem distinct but very short, about 2 mm; leaves 

 lance-ovate to oblong or oval, usually shortly and bluntly acuminate, the 

 upper often obovate-acuminate and larger, forming a rosette, all serrate above; 

 costa narrow, ending below the apex: leaf-cells lax, widely rectangular to hex- 

 agonal: seta short, capsule globose, thin-walled, usually splitting equatorially, 

 brownish, immersed to slightly emergent, obtusely apiculate; spores papillose, 

 .025-. 030 mm, mature in autumn: paroicous; antheridia sessile in upper leaf- 

 axils. 



On wet clayey or sandy soil in fields, along sides of pools, river banks, etc. 

 Europe, Asia, and, in North America, from Quebec to the northern part of 

 eastern United States. Not uncommon in Ohio and also reported from Lan- 

 caster County, Pennsylvania. Not yet reported from our region. 



