232 American Midland Naturalist Monograph No. 6 



2. Hygroamblystegium irriguum (Wilson) Loeske 



(Hypnum irrimium Wilson; Amblystegium irriguum Bryologia Europaea; Hypnum 

 tenax Hedwig — fid. Cardot; Hygroamblystegium tenax Jennings) 



Plate XLIII 



Dark green, aquatic, cespitose: stems rigid, irregularly pinnate, long, 

 denuded at the base, usually with a few paraphyllia at the nodes; stem-leaves 

 ovate to widely triangular lanceolate to triangular — about 1-1.5 mm long, gradu- 

 ally acuminate, acute or sub-acute, narrowed at the base, sub-decurrent, spread- 

 ing and sub-secund, or on the longer branches erect-spreading, entire to 

 sub-serrulate, plane-margined; branch-leaves narrower and tending to lance- 

 ovate; costa thick and wide, yellowish-brown, narrowing and becoming indis- 

 tinct in the acumen but often reaching the apex; median-leaf-cells hexagonal- 

 rhomboid, about 3-6:1, incrassate, often sub-opaque, smaller in the apex, at the 

 base one or two rows usually somewhat enlarged, rectangular, incrassato, often 

 colored, a few rows above these shorter, quadrate, but no distinct auricles 

 being formed: seta about 1.5-2.5 cm long, smooth, castaneous, dextrorse; cap- 

 sule oblong-cylindric, the urn 2-2.5 mm long, 5ub-cernuous and sub-arcuate 

 before ripening to strongly arcuate when dry, smooth, constricted bslow the 

 mouth, bro'ivnish; annulus 3-seriate; lid convex-conic, apiculate; peristome-teeth 

 basally confluent, orange-pellucid and dorsally cross-striolate below, bordered, 

 strongly tra'reculate; the segments slightly shorter than the teeth, carinately 

 split but scarcely gaping, yellowish-hyaline, the 3 cilia nodose, hyaline-papillose, 

 about as lone, as the segments, the basal membrane about two-fifths as high; 

 exotheciai cells small and rounded, hexagonal to transversely rounded at rim 

 but soon becoming rather elongate oblong-hexagonal or rectangular below; 

 spores mature in late spring or early summer, brownish, medium-walled, papil- 

 lose. .016-.019 znm. 



Or\ stones and earth in very wet situations or in water, usually in non- 

 calcareous districts; Europe, Asia, northern Africa, and, in North America, 

 from Ont.irio to California, south to Georgia and Arkansas. 



Now known from Allegheny, Bedford, Butler, Cambria (Porter), Crawford, Erie, 

 Fayette, Huntingdon (Porter), Washington, and Westmoreland counties, and apparently 

 avoiding the upland plateau region. Specimen figured: Hillside, Westmoreland Co., May 

 23, 1908. O.E.J. 



2a. Hygroamblystegium irriguum var. spinifolium (Schimper) Grout 



(H. falldx var. spinifolium Warnstorf; Amblystegium irriguum var. spinifolium 

 Schimper; A. fallax var. spinifolium Limpricht) 



This variety differs from the species in being more robust, with longer 

 stems, longer and narrower leaves, the leaves reaching nearly 2 mm in length 

 and with a strongly excurrent and stout costa: Grout states the upper leaf-cells 

 to be about 6-8:1, and the basal cells more lax. 



Usually in and around calcareous springs and probably distributed mainly 



as is the .species. Ohio, Pennsylvania, New Jersey, and Ontario. 



Butler Co.: On wet cliffs, Winfield Junction. C.M.B. June 8, 1940. Crawford 

 Co.: Pymatuning Sv-famp, Linesville, May 12, 1908. O.E.J. 



