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BFNA | Family List | BFNA Vol. 2 | Hypnaceae | Hypnum

Hypnum depressulum J. K. A. Müller

Plants yellowish to golden green, dark green or dirty brown, regularly to irregularly pinnately branched, usually creeping and firmly affixed by rhizoids, 2--5 cm; branches emerging in plane parallel to substratum, slightly flattened to somewhat julaceous, 0.2--0.4(--6) cm. Stems slender, yellowish to golden green, not hyalodermous, with central strand weakly developed; pseudoparaphyllia lanceolate, infrequent. Leaves falcate-secund, rarely straight, ovate- to oblong-lanceolate, not or weakly decurrent, narrowed into a short acumination that varies from slender to relatively wide; margins serrate distally, serrulate to nearly entire proximally, usually broadly or narrowly recurved proximally but sometimes to the leaf length; costa faint to distinct, rarely single; median cells 30--50 × 4--5 µm, weakly papillose at ends; basal cells broader and often yellowish; alar cells subquadrate or transversely rectangular 8--15(--20) in marginal row, subopaque; stem leaves wider 0.6--1.1 × 0.4--0.6 mm, branch leaves more gradually acuminate and frequently strongly serrate. Sexual condition autoicous; inner perichaetial leaves erect, oblong-lanceolate, with slender serrate acumination, plicate; costa faint or distinct, double or rarely single. Seta yellowish brown to red, 0.7--1.5 cm. Capsule yellowish brown to dark brown, inclined to horizontal, rarely suberect, varying in form and size from oblong to subcylindric, 1--2.3 mm excluding conic operculum, usually curved, annulus 1--2 seriate; cilia of endostome 2--3.

Sporophytes produced summer, capsules mature June--Aug. Rocks, most frequently on boulders, also commonly epiphytic on trees, especially tree bases, mainly in forested areas; 0--2000 m; Alta., B.C., Man., N.B., Nfld., N.W.T., N.S., Ont., P.E.I., Que., Sask., Yukon; Ala., Alaska, Ariz. Colo., Conn., Del., D.C., Ga., Ill., Ind., Iowa, Ky., Maine., Md., Mass., Mich., Minn., Mo., Mont., N.H., N.J., N.Mex., N.Y., N.C., Ohio, Pa., R.I., S.C., S.Dak., Tenn., Vt., Va., W.Va., Wis., Wyo.; Europe; Asia.

Hypnum pallescens occurs from sea level to higher elevations in eastern North America, mainly in forested areas; but in western North America it is less frequent, found from near sea level to subalpine elevations of 2000 m. This species usually produces abundant sporophytes. Hypnum recurvatum is similar in size, but the alar cells are more numerous than in H. pallescens, and the leaves of H. recurvatum are hamate to circinate, but falcate in the latter; pseudoparaphyllia are foliose and mainly 4 or more cells wide in H. pallescens, while those in H. recurvatum are filamentous, often 1-seriate but generally lanceolate. Hypnum recurvatum is mainly a calcicole while H. pallescens is usually a silicole. For additional information, see discussion of Hypnum revolutum var. ravaudii.


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