294 American Midland Naturalist Monograph No. 6 



or more usually nearly horizontal, dorsally gibbous, arcuate, dark-castaneous; 

 lid conic to conic-acuminate; annulus broad, 2-3-seriate; peristome-teeth slender, 

 castaneous below, the apex hyaline and papillose, basally confluent, the lamel- 

 lae and trabeculae closely placed, teeth dorsally cross-striolate, margined; 

 segments slender, about as long as the teeth, yellowish, carinately split; basal 

 membrane about one-half as high as the segments, some of the cilia usually as 

 long as segments, hyaline, nodose, usually 2 or 3; spores usually minutely 

 roughened, somewhat incrassate, brownish, about .01 6-. 020 mm, maturing in 

 early winter. 



In wet places on earth, stones, rotten wood, bases of trees, etc., in shady 

 woods and thickets; Europe, Asia, northern Africa, and, in North America, 

 from Canada to New Jersey and Pennsylvania. 



Rather common in our region. Collected in 1 1 counties widely distributed in western 

 Pennsylvania: Allegheny, Armstrong, Butler, Erie, Fayette, Greene, Lawrence, McKean, 

 Warren, Washington, and Westmoreland. Specimen figured: Wildwood Road Hollow, 

 Allegheny Co., O.E.J. &C G.K.J. Nov. 19, 1908. 



7. Brachythecium rivulare (Bruch) Bryologia Europaea 



{Hypnum rivulare Bruch) 

 Plate LVI 



Robust, cespitose in wide and thick mats, pale golden green, shining, rigid: 

 stems hard and woody, prostrate, filiform, leafless when old; branches irregu- 

 lar on the ascending or sub-erect and somewhat dendroid secondary stems 

 which usually reach a height of 3 or 4 cm; stem-leaves broadly ovate, rather 

 regularly imbricate wh'^n dry, erect -spreading or more open when moist, rather 

 distant, abruptly short-acuminate or acute, concave, decurrent, plicate, denticu- 

 late, reaching about 1.8-2.5x1.0-1.4 mm; branch-leaves similar to the stem- 

 leaves but usually wider, ovate to lance-ovate, decurrent, about 1.5x0.7 mm, 

 quite concave, dentate above, the margins plane or reflexed below, often some- 

 what plicate; median leaf-cells linear, about 10-15:1, prosenchymatous with 

 rounded ends, rather incrassate, the apical shorter, the basal abruptly laxer, 

 shorter, wider, the median basal usually with incrassate and porose walls, the 

 alar abruptly differentiated, more or less enlarged, inflated, hyaline to orange- 

 pellucid, forming distinct and widely decurrent auricles; costa often forking, 

 reaching to the middle or above; seta 1.5-2.5 cm long, strongly papillose 

 throughout, castaneous; capsule castaneous, turgid- to oblong-ovate, about 2- 

 3x1 mm, more or less arcuate, inclined to more or less horizontal; lid conic- 

 acuminate; annulus 2-seriate; exothccial cells at rim small and rounded, below 

 larger and rounded-oblong; peristome-teeth castaneous below, apically hyaline 

 and papillose, basally confluent, strongly trabeculate, distinctly margined by 

 the projecting edges of the cross-striolate dorsal lamellae; segments nearly as 

 lone, carinately split and gaping, yellowish, the basal membrane about one-half 

 as high, cilia 2 or 3, nodose, slender, about as long as the segments; spores 

 smoothish, the walls somewhat incrassate and greenish-brown, about 0.16-0.20 

 mm, maturing in fall. 



