Platylomella

A. L. Andrews

Bryologist 53: 58. 1950.

Endemic
Etymology: Genus name Platyloma and Latin -ella, diminutive, alluding to replaced later homonym
Basionym: Platyloma Kindberg Gen. Eur. N.-Amer. Bryin., 22. 1897,
Synonyms: Sciaromium sect. Platyloma Brotherus
Treatment appears in FNA Volume 28. Treatment on page 319. Mentioned on page 263, 264, 341, 652.

Plants small to somewhat large, dark green to blackish with yellowish green shoot apices. Stems fine, prostrate, irregularly branched or subpinnate; hyalodermis absent, central strand present; paraphyllia present, filiform; rhizoids basal or sometimes adventitious distally on decumbent shoots, forming tomentum, slightly branched, smooth; axillary hair distal cells 1 or 2, hyaline. Stem leaves erect-spreading, straight or incurved, cordate-ovate to ovate-lanceolate, not plicate, 0.5–1.5 mm; base not decurrent; margins plane, serrulate distally or to base, sometimes entire, limbidia conspicuous or sometimes inconspicuous, 2–4-stratose, cells incrassate; apex gradually or abruptly acuminate, sometimes apiculate, tips often obtuse; costa single, strong, percurrent to short-excurrent, usually confluent distally with limbidia; alar cells undifferentiated; basal laminal cells rectangular or oblong-hexagonal; distal cells short-rhomboidal to oblong-hexagonal, 6–12 × 15–40 µm. Branch leaves similar, slightly smaller and narrower. Sexual condition autoicous. Capsule horizontal to cernuous, oblong-cylindric, asymmetric, sometimes arcuate; peristome hypnoid; exostome margins dentate; endostome cilia appendiculate. Spores 12–17(–25) µm.

Distribution

c, e North America.

Discussion

Species 1.

Platylomella has previously been included in Sciaromium (Mitten) Mitten, a synonym of Echinodium Juratzka (S. P. Churchill 1986).