Tritomaria Loeske
Sphenolobus subg. Tritomaria (Schiffn.) Müll.Frib. in Rabenhorst, Krypt.-Fl. Deutschland 6(1): 606. 1910.
Lectotype (Kitagawa, 1966): Tritomaria exsecta (Schmid. ex Schrad.) Loeske (≡Jungermannia exsecta Schmid.)
Plants prostrate and with ascending apices to (with crowding) suberect to erect, pure green or brownish tinged or reddish or purplish brown or purplish black. Branching sparingly, the branches predominantly of Frullania type, at times of Radula type; lateral-intercalary branches present in some species; geotropic, microphyllous stolons and flagellae lacking. Stem with cortex firm, sometimes strongly thick-walled, in 1–2(3) strata; medulla dorsiventrally differentiated, the ventral strata of smaller cells that eventually become brown and mycorrhizal, the dorsal strata free of fungi. Rhizoids copiously produced, except sometimes toward shoot apices. Leaves vertically or subvertically oriented, widely spreading, the dorsal half of insertion transverse or inclined toward stem apex or ( var. novaezelandiae) often becoming weakly succubous, the insertion extending to the stem midline dorsally and often decurrent; leaves dorsally assurgent, concave to canaliculate, typically (2)3(4)-lobed (in var.novaezelandiae 2–3-lobed, the 2- and 3-lobed leaves of about equal frequency), often asymmetrically so, with the third, dorsal lobe displaced basally and shorter than the 2 subequal ventral lobes; lobes sharp, at times cuspidate, entire (except Tritomaria heterophylla, where sometimes dentate), the apices at times becoming erose from gemmae formation; margins entire, never developing cilia at the base. Cells with walls firm, the median cells with trigones usually bulging; median and basal cells away from marginal sectors often conspicuously elongated; surface weakly to distinctly papillose or (in ours) striate throughout. Oil-bodies (Schuster, 2002a) medium-large, usually 4 or more per cell, finely botryoidal or granular-botryoidal. Underleaves absent; ventral merophytes obsolete, at most 2 cells broad. Asexual reproduction by gemmae rare to ubiquitous, the gemmae yellowish brown to golden to reddish brown or red, elliptical or polygonal, 2-celled at maturity.
Dioecious. Androecia intercalary, the bracts leaf-like except concave to moderately ventricose at base; antheridia usually 2–4 per bract, the stalk 1- or 2-seriate. Gynoecial bracts usually nearly leaf-like and commonly lobed like the leaves or with 1–2 accessory lobes, often broader or sometimes (Tritomaria heterophylla) ciliate-dentate; bracteole absent or (at least in T. scitula) narrow, oblong, connate for most of its length with 1 bract. Perianth cylindrical-obovoid, rather deeply plicate above the middle, gradually contracted to the mouth, the mouth considerably ( subg. Tritomaria) or hardly so ( subg. Saccobasis), the mouth entire or dentate-ciliate.
Seta of numerous cells, unspecialized. Capsule wall 3–5-stratose; outer layer of cells with nodular thickenings; inner layer of cells with semiannular bands.
A basically Laurasian genus with some eight species belonging to three subgenera; for details of the distribution of the species see Engel (2006a). One species is bipolar and occurs in our area.
The generic description is adapted and modified from Schuster (1969b).
References: Engel (2006a); Kitagawa (1966); Schuster (1969b, 2002a).
