Rhacomitrium crispipilum

Rhacomitrium crispipilum

Rhacomitrium crispipilum (Tayl.) Jaeg., Ber. S. Gall. Naturw. Ges. 1872–1873:96, 1874 (Ad. 1:374).

Trichostomum crispipilum Tayl., Lond. J. Bot. 5:47, 1846. [Original material: Summit of the Quitinian Andes, Ecuador, coll. Jameson, 1845.]

Rhacomitrium striatipilum Card., Bull. Herb. Boiss. ser. 2, 5:1004, 1905. [Original material: Tierra del Fuego, Tekenika Bay, coll. Skottsberg n. 74; Ushuaia, coll. Skottsberg n. 83 in part.]

Rhacomitrium integripilum Dus., Ark. Bot. 6(10):20, 1907. [Original material: Desolation I., Puerto Angosto, Magellan Straits; Río Aysen, western Patagonia, both coll. Dusén, 1895–1897.]

Rhacomitrium geminatum Roiv., Arch. Soc. Zool. Bot. Fenn. Vanamo 9:88, 1955. [Original material: Fjordo de Finlandia, western Tierra del Fuego, Coll. Roivainen, 1928–1929.]

Rhacomitrium substriatipilum Roiv., Arch. Soc. Zool. Bot. Fenn. Vanamo 9:95, 1955. [Original material: Cerro Nylandia, Fjordo Finlandia, western Tierra del Fuego, coll. Roivainen n. 1800.]

Plants in dense, spreading mats with stems to 6 cm long, numerous lateral branches. Leaves lanceolate, 3–4 mm long, ca. 1 mm wide, usually laxly imbricate, rapidly recurved and spreading when moist; hyaline hair 0.5–1.5 mm long, non-papillose, usually denticulate; leaf margins entire or minutely crenulate, narrowly recurved at base; base weakly plicate; costa disappearing into base of hyaline tip, ca. 75 μm wide at base, ca. 50 μm wide distally; lamina cells unistratose throughout, smooth to transversely striate; upper cells variable, sometimes many short, about twice as long as wide; lower cells up to 80 μm long, wall thickenings confluent in thickened band, lumens usually very narrow; alar cells short-rounded, in 1–2 rows in short decurrency, a row of thin-walled cells expending up the margin. Setae 6–10 mm long, often in pairs. Spores 11–15 μm in diameter.

MAS AFUERA: Ridge above Q. Pasto, c. 1250 m, Sk. 142.

The species is widely distributed in the southern hemisphere, occurring in southern South America, New Zealand, and Kerguelen, and extending northward to the northern Andes, Central America, Hawaii, New Guinea, and the Himalayas. Related species include R. heterostichum (Hedw.) Brid., of the north, which was distinguished by Dixon (1913–1929) by its consistent lack of the row of hyaline cells along the basal margin, and R. crispulum, of Antarctica and the subantarctic islands, which has little or no hyaline leaf tip, shorter setae, and no fasciculate branching.

The need for further subdivision remains in question. In the present concept I include many plants with variously weak basal plications, striated upper cells, and entire-margined hair tips on the leaves. Such characters are the basis for some Roivainen species, but variations are seen in individual plants. A more reasonable subdivision has been made between the coarse, more erect specimens of the subantarctic and Juan Fernandez that are R. striatipilum, and the more lax material with frequent twin setae that would be typical of the widely distributed R. crispipilum (= R. geminatum Roiv.)