82 American Midland Naturalist Monograph No. 6 



urceolate; peristome none; operculum v/ith a long and oblique rostrum at least 

 two-thirds the length of the urn, the operculum often remaining attached to 

 the columella for some time after the spores have been shed; spores yellowish, 

 moderately incrassate, smooth, about .014-017 mm in diameter, mature in 

 September or October. 



Not uncom.mon on wet cliffs, principally calcareous, in Europe, Asia, 

 northern Africa, and, in North America, from Alaska to Labrador south to 

 California and the Carolinas. 



Allegheny Co.: Guyasuta Hollow, Aspinwall, on wet cliff near waterfalls, October 

 12 and 25 (figured) 1908, and September 8, 1909. O.E.J. Butler Co.: On cliff, Win- 

 field Jet., Buffalo Creek. June 8, 1940. C.M.B. Lawrence Co.: On wet face of 

 exposure of the Homewood Sandstone, near Rock Point, October 15, 1910. O.E.J, and 

 G.K.J. Somerset Co.: Vicinity of Trent. Aug., 1932. Chas. M. Hepner. 



5. Trichostomum Bruch 



Dioicous, rarely autoicous: densely cespitose, medium size, green to yel- 

 lowish-green: stem with central strand, erect, radiculose, rarely felted, densely 

 leaved, mostly dichotomously branching; leaves spreading, mostly crisped when 

 dry, upper leaves much the larger, long and narrow, more or less concave to 

 canaliculate, margins mostly erect to involute, often undulate, mostly entire; 

 costa well-developed, sometimes ending below the apex or excurrent; upper 

 leaf-cells small, rounded, chlorophyllose, papillose on both faces, towards the 

 base elongated-rectangular, mostly hyaline: seta long, erect; capsule erect, 

 rarely inclined, mostly symmetric, oblong-cylindric to cylindric, short-necked, 

 rarely strumose; basal membrane of peristome low or none, the teeth 16, erect, 

 smooth or papillose, red or yellow, undivided or cleft into two filiform non- 

 articulated divisions which are sometimes approximate in pairs; spore small; 

 lid conic, rostrate, the exothecial cells of the base in vertical series or rarely 

 dextrorsely ascending; calyptra cucullate, smooth. 



A genus of about 80 species, v/idely distributed on earth and rocks. Sev- 

 eral species in North America; only one in our region. 



1. Trichostomum cylindricum (Bruch) C. Mueller 



(Didymodon cylindricus Bryologia Europaea; T. tenuirostre Lindberg) 



Plate XVI 



Rather loosely and softly cespitose, yellowish, dark below: stems erect 

 branching, rather flexuous, reaching to 1.5-2 cm in height; leaves about 2-3 mm 

 long, narrowly linear-lanceolate, when dry crisped and contorted, when moist 

 spreading or flexuous, gradually acuminate or sometimes rather abruptly nar- 

 rowed on an acute apex, the margin papillose-sinuate, plane or involute; basal 

 leaf-cells elongate-rectangular or more or less angular-oblong, somewhat in- 

 flated, hyaline in a broad band that does not extend up the margin, above 

 rather abruptly becoming much smaller, incrassate, quadrate to rounded- 

 hexagonal, the median and upper rounded-quadrate to rounded-hexagonal or 

 transversely oblong, densely papillose, much incrassate; costa strong, usually 

 forming the apex of larger pellucid cells: seta single or sometimes in pairs, 



