Trichocolea Dumort.
Type: Trichocolea tomentella (Ehrh.) Dumort. (≡Jungermannia tomentella Ehrh.)
Plants loosely procumbent, less often creeping or pendulous, pale yellowish to whitish green, becoming almost whitish when dry, typically vigorous. Branching usually (1)2–3(4)-pinnate, the branches all of Frullania type, never becoming flagelliform and microphyllous. Stems rather fleshy, often paraphyllose, the cortex ill-defined, somewhat smaller than the thin-walled medullary cells. Rhizoids rare or lacking, restricted to underleaf bases. Leaves contiguous to loosely imbricate, usually distinctly succubous, asymmetric, the dorsal lobe(s) somewhat smaller and the dorsal sector of disc somewhat lower, usually obtrapezoidal to subreniform in outline, deeply (3)4-lobed, the principal lobes usually with numerous secondary, smaller lobes, the lobes ultimately becoming resolved into a cobwebby mass of tapered cilia; cilia uniseriate, formed of strongly elongated cells, opposed or verticillate in groups of three; disc on one or both margins often with an accessory lobe or lobes. Cells often at least locally tiered, everywhere narrow and rectangular, those of disc thin- to weakly firm-walled and with trigones absent, those of cilia longer; surface of lobes papillose-striolate, becoming striolate toward disc base. Oil-bodies small, ranging up to 15(20), finely granular to irregularly granular-papillose. Underleaves somewhat smaller than leaves, symmetrical, bifid, the lobes again bifid and the underleaves then bisbifid, or (T. rigida) quadrilobed, the margins armed as in leaves. No asexual reproduction.
Dioecious. ♂ Branches similar to vegetative branches; bracts in 12–15 or more pairs, leaf-like except the disc concave and higher and the lobes shorter; antheridia 1–2 per bract. Gynoecia terminal on main shoots (but often secondarily displaced to one side because of vigorous growth of a subgynoecial branch); bracts and bracteoles inserted at or below coelocaule base, similar to leaves and underleaves except larger and more copiously lobed and ciliate; bracteoles like underleaves, but larger. Coelocaule prominent, developing with fertilization, clavate to obpyriform, the wall polystratose, hispid in appearance, covered by ± reduced bractlets and variable paraphyllia, a perianth lacking; calyptra absent, the unfertilized archegonia remaining hidden among the mass of paraphyllia at coelocaule summit, the develop- ing sporophyte deeply boring into shoot apex and protected entirely by stem tissue (i.e., the coelocaule).
Seta long, massive, often hollow with maturity. Capsule ellipsoidal (the length:width ratio 2–2.5:1), the wall (5)6–8-layered, the outer layer of cells large, hyaline, usually lacking pigmented wall-thickenings; innermost layer of cells with nodular to spine-like thickenings that often extend across the free tangential walls as complete semiannular bands.
Spores granular, 1.3–2× elaters in diam. Elaters bispiral.
Key to Species
A genus of ca. 20 species, most of which are tropical montane. Six are Neotropical, and six are Paleotropical in distribution; New Guinea has three species: Trichocolea fragillima Herzog, T. gracillima Austin and T. pluma (Reinw., Blume & Nees) Mont. The last has the broadest distribution, ranging from New Guinea to the Philippines to Asia. While the Neotropical species were revised by Hatcher (1959), the Paleotropical taxa await taxonomic study. One species, T. tomentella (Ehrh.) Dumort., is basically suboceanic–oceanic over a broad range in temperate areas of the Northern Hemisphere. Three species occur in New Zealand, and, interestingly, the only southern temperate members of the genus are Australasian. The southern South American T. elegans Lehm. has been transferred to Leiomitra by Hässel (2002).
References: Hatcher (1958; rev.); Stewart (1978; oil-bodies of T. mollissima); Taylor and Hollensen (1970; studies of ♀ inflorescences); Schuster (1968b, 2000a, 2001d).
