258 American Midland Naturalist Monograph No. 6 



of trees, usually confined to mountainous regions; Europe, Asia, northern 

 Africa, and, in North America, from Nova Scotia to Ontario and south in the 

 mountains to Georgia; Missouri. 



It is probable that deforestaion and lumbering activities have largely so 

 modified the environment that this species is becoming rare. Most of the col- 

 lections recorded were made prior to 1900. 



Rather common in our region. Known from Beaver (Porter), Blair (Porter), Cam- 

 bria (Porter), Clinton, Elk (Porter), Fayette, McKean, Somerset, Warren, and Wash- 

 ington (Porter) counties. Sfjecimen figured: Densely shaded rocks, Marilla Brook, 

 Bradford, McKean Co., April 25, 1895. D.A.B. (This was distributed in Grout's 

 N. Am. Musci Pleurocarpi, No. 44). 



17. Hypnum Linnaeus, Hedwig 



Dioicous: robust, stiff, deeply and loosely cespitose, dark to pale green or 

 almost straw-colored, more or less lustrous: from a decumbent base ascending 

 to erect, with straight pointed ends and rather regularly pinnate; branches 

 mostly spreading and 2-seriate, usually slenderly attenuate, sometimes thick, 

 julaceous, and obtuse; no paraphyllia; leaves crowded, imbricately appressed, 

 spoon-shaped, more or less distinctly plicate, scarcely decurrent, broadly ovate 

 to ovate-oblong, apex blunt, the margin often narrowly revolute below and 

 broadly involute upwards, at the very apex only weakly crenulate or serrulate; 

 costa indistinct, or very thin, short and double; median leaf-cells narrowly 

 prosenchymatous, smooth, the basal shorter, laxer, porose, incrassate, yellowish 

 to orange-red, the alar abruptly enlarged, quadrate to shortly rectangular, or 

 several-angled, incrassate, colored, the alae more or less excavate; perichaetial 

 leaves sheathing, lance-oblong, rather abruptly acuminate, indistinctly costate: 

 seta 2-4 cm long, sinistrorse, tortuous, yellowish-red to red; capsule cernuous, 

 2-2.5 mm long, usually horizontal, symmetric, or dorsally somewhat gibbous, 

 drying arcuate, slightly constricted below the mouth, brownish, smooth; annu- 

 liis none; lid high-convex, acute or conic-obtuse. 



The genus is variously delimited by different authors; as here restricted it 

 contains only the following species. 



1. Hypnum Schreberi Willdenow, Schwaegrichen 



{H. parietinum Linnaeus; H. muticum Swartz; Stereodon Schreberi 

 Mitten; Hylocomium parietinum Lindberg) 



Plate XL VIII 



Usually bright yellowish-green: stems up to 12 or 15 cm long, bright red; 

 stem-leaves 1.5-2.5 mm long; median leaf-cells about 10-15:1, the apical 

 shorter: cp.psules produced rather infrequently; exothecial cells transversely 

 oblong-hexagonal, laterally strongly castaneous-incrassate; peristome-teeth slen- 

 der, strongly trabeculate, dorsally lamellate, faintly transversely papillose- 

 striolate, margined, yellowish, confluent below; segments broad, nearly as long 

 as the teeth, widely carinately gaping, yellowish and papillose; cilia sub- 

 appendiculate, about as lona as the segments, usually single; the basal mem- 



