8. CALYMPERASTRUM Plate 9.

Calymperastrum Stone, J. Bryol. 14: 315–318, 1986. Type: Calymperastrum latifolium (Hampe) Stone.

Plants in a low turf, yellowish green above, yellowish brown below. Stems not branching, ca. 6 mm in length, transverse section rounded-pentagonal to triangular, central strand distinct, generally with an satellite strand just below the sclerodermis, sclerodermis of 1–2 layers of thick-walled cells, hyalodermis weakly developed in patches; axillary hairs ca. 6 cells in length, all hyaline; papillose, reddish brown tomentum on lower part of stem. Leaves spreading-incurved and conduplicate from an appressed base when dry, spreading when moist, long-spathulate, 2.0–3.1 mm in length, upper lamina broadly concave, margins plane to weakly incurved above, entire, bistratose in 1(–3) rows from shoulder to 3/4 length of leaf, cell walls of border slightly thickened; apex rounded-acute and bluntly apiculate; base strongly differentiated in shape in lower 1/3 of leaf, cuneate, with distinct shoulders, basal cells narrower along margins; costa strong and tapering above, percurrent, superficial cells quadrate to short-rectangular and papillose ventrally, elongate and weakly papillose dorsally, 4–6 rows of cells across costa ventrally at midleaf, costal transverse section nearly round, stereid bands two, usually strong ventrally (the cell walls often thicker than those of dorsal band, especially in sections made through leaf base) and generally larger than the dorsal, distinct to nearly absent dorsally, epidermis well differentiated ventrally but absent dorsally, guide cells small and 4 in 1 layer, hydroid strand strong, in a central position just dorsal to the guide cells and often also ventrally; upper laminal cells subquadrate to 5– or 6–sided, often slightly longer than wide, 9–13 µm in width, 1(–2):1, walls thin to weakly evenly thickened, superficially strongly bulging ventrally, less strongly bulging dorsally; papillae small, crowded, bifid, solid, ca. 8 per lumen; basal cells strongly differentiated from upper cells, rising higher and larger medially, weakly inflated, rectangular, ca. 20 µm in width, 2–4:1, walls thin, hyaline, lacking internal or superficial pores. Sexual structures and sporophyte unknown. Laminal KOH color reaction yellow.

A monotypic genus endemic to western Australia, growing on cycads.

This genus can be excluded from the Calymperaceae mainly by the hydroid strand (Pl. 9, f. 9) in the leaf. It appears to have many of the characteristics of Bryoerythrophyllum and Mironia (especially those of the areolation), but it differs markedly in being yellow in KOH. From Dialytrichia, which also has a bistratose leaf margin (Pl. 9, f. 7), it differs in its broadly concave ventral laminal surface (not deeply grooved along the costa), its plane leaf margins (not recurved below midleaf), its round (not semicircular) costal section and semicircular (not crescent-shaped) section of dorsal stereid band. Calymperastrum is also somewhat like Trichostomum especially in the plane to incurved margins but a hydroid strand is rare in that genus, and the only Trichostomum species seen with a bistratose leaf margin, T. marginatum, only doubtfully belongs to Trichostomum.

Calymperastrum is also like certain species of Leptodontium (e.g. L. stoloniferum) in the leaf shape and strongly differentiated basal cells, but the presence of a central strand, a hydroid strand and a differentiated costal epidermis are not characters of Leptodontium. Transverse sections of the stem show satellite strands just interior to the sclerodermis, usually one per section and correlated with a broad stem ridge decurrent from each costa. The satellite strand appears to be a leaf hydroid strand (these being unusually strong in Calymperastrum) extending into the central cortex but not reaching the stem central strand (Pl. 9, f. 2). Aloinella, an unrelated taxon, has a similar stem morphology. A more thorough description of the genus is given by Stone (1986), who saw additional material.

This monotypic genus appears to be, like Hypodontium, transitional in morphology between the Pottiaceae and the Calymperaceae, approaching the latter through the following combination of characters: arboreal habitat, leaves with rounded apices and plane, thickened margins, costa percurrent, ending in an apiculus, the ventral stereid band of cells with walls more strongly thickened that those of the dorsal (cf. Syrrhopodon richardsii Dix.), upper laminal cells more strongly bulging ventrally than dorsally, basal cells strongly differentiated from the upper cells (but not as sharply demarcated as is usual in Calymperes and Syrrhopodon), and laminal KOH reaction yellow. The ventral stereid cells being more strongly thickened than those of the dorsal band is a character not found elsewhere in the Pottiaceae, but is apparently occasional in the Calymperaceae. The only unique character to my knowledge distinguishing Calymperastrum from genera of the Calymperaceae is the presence of a leaf hydroid strand. Other characters cited in the original description (Stone 1986) as indicative of Pottiaceae are also found in various genera of both the Calymperaceae and the Pottiaceae, including the stem central strand, papillae on the upper cells of the sheathing leaf base, bifid papillae on both surfaces of laminal cells, and absence of foliar gemmae. The significance of the presence of seriate papillae on the dorsal costal surface cannot be evaluated here, and information on the sporophyte is lacking.

Number of accepted species: 1.

Species examined: C. latifolium (MELU).