Tropicos | Name - !Gymnostomum aeruginosum Sm.

Cent. Amer. Moss > Pottiaceae > Gymnostomum > Gymnostomum aeruginosum

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!Gymnostomum aeruginosum Sm.

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Project Name Data (Last Modified On 2/15/2011)

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Project data (Last Modified On 2/15/2011)

Discussion:

Gymnostomum aeruginosum, a small plant with a pale-greenish color, is restricted in Central America to Guatemala. Distinctive features of the species include its stem central strand, narrowly lanceolate leaves with plane leaf margins, firm-walled upper and lower leaf cells that have simple, scattered papillae and subpercurrent costae that end 2–5 cells below the apex. The species often has obtuse leaves, although forms with acute leaves are also encountered. Unlike more northern material of the species, in Central America the leaves of G. aeruginosum lack a ventral stereid band. Hymenostylium recurvirostrum is sometimes placed in Gymnostomum (Crum & Anderson 1981, Ireland 1982) and it can be difficult to distinguish from G. aeruginosum. It differs from G. aeruginosum in lacking a stem central strand, having recurved lower leaf margins, often porose leaf cells, and systylius capsules.

Molendoa sendtneriana and Anoectangium aestivum can also be confused with G. aeruginosum. Molendoa sendtneriana is usually distinguished from G. aeruginosum by its more narrowly acute leaves that are weakly keeled above, and have more heterogeneous upper leaf cells with massive, fused papillae. There are, however, small, reduced plants of Molendoa sendtneriana with rounded leaves, more or less plane leaves, and low simple papillae that are very difficult to distinguish from G. aeruginosum. Plants of G. aeruginosum can be separated from this expression of M. sendtneriana by their less-developed ventral stereid band in the costa, more homogeneous upper leaf cells, terminal perichaetia, and the present of sparsely distributed, massive red rhizoids. Anoectangium aestivum is best distinguished from G. aeruginosum by its keeled leaves and deeply grooved costa that is only two cells wide at the ventral surface. Zander (1977) provided an in-depth treatment of G. aeruginosum and its relationships.

Illustrations: Grout (1939, Pl. 91 D); Bartram (1949, Fig. 39); Zander (1977, Figs. 47–60); Crum and Anderson (1981, Fig. 125); Ireland (1982, Pl. 104); Noguchi (1988, Fig. 118 B, as G. calcareum); Gao (1996, Fig. 49 1–5); Zander (1993, Pl. 46 1–9); Sharp et al. (1994, Fig. 184 a–g). Figure 32.

Habitat: On calcareous boulders and trail side banks, rarely on tree trunks; 1700–2500 m.

Distribution in Central America: GUATEMALA. El Progreso: Sharp 5099 (F, FH); Guatemala: Standley 62866 (F); Huehuetenango: Standley 65661 (F); Quiché: Sharp 2494 (FH); Sacatepéquez: Standley 58936 (F).

World Range: Subarctic America, Western and Eastern Canada; Northwestern, North-Central, Northeastern, Southwestern, South-Central, and Southeastern U.S.A.; Mexico; Central America; Caribbean, Western, Northern and Southern South America, Brazil; Northern, Middle, East, Southwestern, and Southeastern Europe; Siberia, Russian Far East, Caucasus, Middle Asia, Mongolia, China, Eastern Asia, Western Asia, Arabian Peninsula; Macaronesia, Northern Africa, East and South Tropical Africa, Southern Africa; Indian Subcontinent, Indo-China, Malesia; Australia, New Zealand; Southwestern Pacific.

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Gymnostomum aeruginosum Sm., Fl. Brit. 3: 1163. 1804.

Trichostomum aeruginosum (Sm.) Lindb., Öfvers. Förh. Kongl. Svenska Vetensk.-Akad. 21: 229. 1864. Mollia aeruginosa (Sm.) Lindb., Musci Scand. 106. 1879. Eucladium aeruginosum (Sm.) C. Jens., Danmarks Mosser 2: 313. 1923. Protologue: Wales. Gathered in North Wales by J. W. Griffith Esq.

Anoectangium arizonicum Bartr., Moss Fl. N. Amer. 1(3): 192. 1938. Protologue: U.S.A. Arizona: ledges back of Daly’s mine, White House Canyon, Santa Cruz Co. Alt. about 6,500 ft. [E. B. Bartram 919] (FH).

Plants small and slender to medium-sized, forming tufts or caespitose, yellowish green to pale-green, saxicolous or terricolous. Stems 2–20 mm long, smooth, branching irregularly, sclerodermis and central strand usually present; rhizoids dimorphic: slender, red, smooth, branched ones scattered on the stem and massive, red, roughened, sparsely branched ones originating in leaf axils. Leaves somewhat distant and evenly spaced, wide‑spreading when wet, appressed when dry, apex contorted, ligulate to linear-lanceolate, 0.6–1.0 mm long; apices acute to obtuse or sometimes rounded; margins plane, entire to crenulate; costa ending just below apex, narrow, dorsal and ventral surfaces papillose, guide cells present, ventral stereid band not present in Central American material but weakly developed in robust collections outside the region, dorsal stereid band present, ventral surface cells enlarged, dorsal surface cells smaller than laminal cells and strongly thickened; upper leaf cells somewhat heterogeneous, rounded to quadrate sometimes transversely rectangular, 8–10 μm long, 1:1–2 (length:width), walls weakly thickened, papillose on both surfaces by scattered, low papillae, basal cells homogeneous, short-rectangular, 2–3:1 (length:width), thin-walled, smooth, marginal cells not differentiated, alar cells not differentiated. Gemmae in leaf axils. Dioicous. Perigonia terminal, geminate. Perichaetia terminal. Setae 4–6 mm long, yellow, smooth. Capsules exserted, erect, short-cylindrical, 0.5–0.8 mm long, smooth, brown; stomata in neck; opercula rostrate, beak erect, 0.5 mm long; peristome absent. Spores 9–12 μm, round, granulate, brown. Calyptrae cucullate, 0.7–1.0 mm long, smooth.