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FNA | Family List | FNA Vol. 27 | Dicranaceae

1. Aongstroemia Bruch & Schimper, Bryol. Europ. 1: 171. 1846.

[For Johan Ångström, 1813-1879, Swedish bryologist]

Patricia M. Eckel

Plants small, gregarious or in loose thin mats or tufts, yellowish green, orange-red to brown-green, rather dull. Stems erect, 3-6(-12) mm, simple or occasionally forked, central strand present; scarcely radiculose, rhizoids red, smooth. Leaves ovate or shortly lanceolate-acuminate, concave proximally, tubulose when acuminate, erect and appressed-imbricate when dry, somewhat loosely so when moist; apices in proximal leaves broadly acute grading to obtuse to acuminate-subulate in distal leaves; margins plane to incurved, entire, notched at the apex; costa prominent, single, ending before the apex, smooth on all surfaces, guide cells in 1 row, stereid bands 2, the adaxial band reduced, abaxial and adaxial epidermis prominent; laminal cells convex in section, without pits, smooth, mostly elongate throughout, shorter in the apex, walls in surface view thick-walled, irregularly elongate-hexagonal, rhomboid or rectangular, alar cells undifferentiated. Specialized asexual reproduction absent. Sexual condition dioicous; perigonial plants similar to the perichaetial, perigonium terminal, conspicuous, perigonial leaves larger than the cauline leaves, broadly lanceolate-triangular with an abrupt acumination, broadly tubulose; perichaetium terminal, conspicuous, leaves larger than stem leaves, convolute-sheathing, abruptly long-acuminate to subulate. Seta elongate, smooth, erect, yellow-orange to red. Capsule erect, globose, ovate or short-cylindric, straight, symmetric, smooth wet or dry, annular cells weakly differentiated in one layer; operculum conic to short-rostrate, oblique; peristome variably absent or present, single, 16 teeth ± cleft to 1/2 the length, vertically pitted-striolate basally, weakly papillose to smooth distally, reddish brown to nearly hyaline. Calyptra cucullate, smooth, naked, fugacious. Spores 12-20 µm, smooth to finely papillose.

Species 7 (1 in the flora): North America, Mexico, Central America, South America, Eurasia, Atlantic Islands.

Aongstroemia is found in north-temperate and tropical areas. The julaceous gametophyte of Aongstroemia species often has been compared to similar habits of other genera, e.g., A. J. Grout’s (1928-1940, vol. 1) statement, seconded by H. A. Crum (1994b), that Aongstroemia has the habit of an Anomobryum (Bryaceae) but the peristome of a Dicranum. The genus Aongstroemia highlights the rather poor differentiation of Dicranaceae from the Ditrichaceae. The latter has “peristome teeth that are divided into terete rather than flat divisions and lack vertical pit-striations” (H. A. Crum and J. A. Snider 1994). Among the genera discussed below, the only consistent distinction afforded Aongstroemia is the dioicous sexuality. Eperistomate species of Aongstroemia in Mexico, Central America, and South America may be confused with species in Astomiopsis Müller Hal., which also has julaceous stems, similar leaves, areolation and spores (smooth to faintly papillose) but lacks a peristome. Astomiopsis has autoicous rather than dioicous inflorescences, and the rather well-differentiated annulus in two rows is characteristic (J. A. Snider 1994c). Monotypic Bryomanginia Thériot, without a peristome, is also autoicous, with a prominent annulus, distally bistratose leaf laminae, fastigiately branched habit, and bipolar ornamented spores (proximally vermiculose, distally rugose) (J. A. Snider 1994d). An informative discussion of these genera has been given by W. R. Buck and R. H. Zander (1980).

The highest diversity for Aongstroemia is in Mexico, Central America, and South America.

Lower Taxon


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