Flora of New Zealand Series

Tritomaria exsecta (Schrad.) Loeske subsp. novaezelandiae Engel, Bryologist 109: 61. f. 1, 2. 2006. 

Holotype: New Zealand, South Is., Nelson Prov., St. Arnaud Ra., Rainbow Skifield just below skitow area, E of S end of Lake Rotoiti, S of St. Arnaud, 1210 m, Engel 22800 (F); isotype: (CHR).

[Figs. 144, 145]

Plants rather stiff, brittle (both stems and leaves), loosely creeping, the distal sector of shoots stiffly ascending, the shoot apices distinctly and sharply curved upward, the plants pale green, at times tinged with pale brown, medium in size, to 1.5 mm wide. Branching sparing, irregular, the branches lateral-intercalary, from the median sector of leaf axils; Frullania -type branches present, occasional. Stems rather stout for plant size, the cortex in 2–3 rows of firm-walled, smaller cells, the cortical cells in ventral half of stem with mycorrhizal infection, with exposed wall distinctly thickened and orange-brown; medullary cells thin-walled, differentiated dorsiventrally, the ventral layers of small cells strongly mycorrhizal, the dorsal layers of large cells lacking fungi. Rhizoids frequent, even at shoot apex, rather short for plant size, scattered, but with a tendency for formation of fascicles at ventral leaf bases, the rhizoids reddish brown toward bases, colorless distally. Leaves rigid, strongly dorsally assurgent, the entire leaf widely spreading or the ventral half of leaf (+ ventral-most lobe) widely spreading and the dorsal sector incurved and becoming suberect, the leaves then weakly conduplicate (but never with a sharp keel or fold), the leaves approximate to loosely imbricate, strongly succubously oriented (appearing weakly succubously oriented when dorsal margin suberect), the insertion strongly succubous for most of its length, often becoming weakly succubous to subtransverse at dorsal end; leaves rather strongly concave, suborbicular to oblate, often asymmetric and then with the ventral sector somewhat dilated resulting in the ventral margin becoming distinctly longer, the leaves 665–805 µm wide × 575–630 µm long to 775–980 µm wide × 700–915 µm long, 1.05–1.5× wider than long, shallowly 2–3-lobed to 0.1–0.2, the lobe number variable, inconsistent, the 2- and 3-lobed leaves of about equal frequency, the lobing at times asymmetric, the ventral lobe somewhat larger, with continued gemmae production the lobe apices becoming increasingly erose, irregular, and the lobe number obscured, at times the leaf apices even appearing undivided and obtuse; lobes (lacking gemmae formation) medium to rather broadly acute, terminating in a single cell or a uniseriate row of 2 cells, the tip cells ± isodiametric, the lobes at times terminating in a pair of laterally juxtaposed cells, the lobe margins entire; sinuses ± narrowly rounded; lamina margins entire, the dorsal strongly and broadly arched, narrowing toward the base, the ventral margin arched similarly to the dorsal or, more often, more strongly so, subcordate at the base. Cells in median sector of leaf thin-walled, trigones distinct, straight-sided to slightly bulging, the median cells very small, subisodiametric, 11–14 µm wide and long; cells toward apex, margins and base evenly thick-walled, with trigones absent or small and concave-sided; median basal cells somewhat larger, 12–18 µm wide × 20–25 µm long; surface striate throughout, even at leaf apex, the median cells with 2–5 striae per cell, some extending the length of 2–4 cells. Underleaves (even rudimentary) totally lacking. Asexual reproduction by gemmae, the gemmae copiously produced, reddish brown, basically smooth, broadly elliptic, often irregularly so, often attached to one another in groups of 2 or 3, the gemmae 2-celled, 10.1–11 × 16.3–17.3 µm; gemmiparous shoots not strongly ascending, the leaves with prolonged gemmae formation not smaller in size. Fungal partner a basidiomycete.

Androecia and gynoecia unknown.

Distribution and Ecology : Tritomaria exsecta is bipolar (see Engel, 2006a).  Subspeciesexsecta is widespread and common in virtually the entire temperate/subarctic sectors of Laurasia, in the New World occurring south to Mexico (2000–3000 m), in Africa known from the high volcanoes of East Africa, the Sani Pass (Natal) on the border with South Africa, and Ethiopia (for details see Engel, 2006a).

 Subspeciesnovaezelandiae is known only from the type, which was found growing over rock of a vertical cliff face in a steep-sided, narrow stream valley with nearly vertical cliff-like sides in a Nothofagus solandri var. cliffortioides forest.

Comments : Tritomaria exsecta subsp. novaezelandiae may be recognized by several characters. Plants are pale green and develop brownish pigmentation, and the branches are of the lateral-intercalary and Frullania types (Fig. 144: 1; Fig. 145: 2). The leaves are 2–3-lobed, with lobe number in about equal frequency (Fig. 144: 1, 3–9), and the dorsal lobe is always smaller. The leaves are notably concave (Fig. 144: 1, 2; Fig. 145: 1, 2), and the leaf insertion is succubously oblique for most of its length, but transverse to subtransverse to weakly succubous at the dorsal third (Fig. 144: 1, 2; Fig. 145: 2). Areolation is distinctive: leaf cells are small, subisodiametric and only 11–14 µm wide and long, with well-developed trigones, but the cells toward the apex, margins and base tend to be evenly thick-walled, with trigones absent or somewhat developed (Fig. 145: 3, 4, 6). The leaf surface is distinctly striate throughout, i.e., even toward the leaf apex (Fig. 145: 6, 8). Reddish brown gemmae are copiously produced and are basically smooth, broadly elliptic and 2-celled (Fig. 144: 11). Stem medullary cells are dorsiventrally differentiated with strong mycorrhizal infection (Fig. 144: 12).