Herbertus Gray
Herbertus Gray, Nat. Arr. Brit. Pl. 1: 678, 705. 1821.
Sendtnera Endl., Gen. Plant., Suppl. 1: 1342. 1840.
Herpocladium Mitt. in Seem., Fl. Vit. 405. 1873 (1871).
Type: Herbertus aduncus (Dicks.) Gray (≡Jungermannia adunca Dicks.)
Plants green to more often stramineous brown to deeply reddish brown, the leafy stems small to robust, often with the facies of a moss, ranging from 2 up to 25 cm long; plants at times developing a system of basal, prostrate, rhizomatous, microphyllous stolons from which arise ascending to erect (often pendulous in epiphytic species), typically unbranched, leafy shoots. Branching ventral-intercalary, very rarely lateral-intercalary. Stems rigid, brittle, the cortex well differentiated, in 2–4 layers of thick-walled cells each often with a reduced lumen; medullary cells thinner-walled, becoming gradually larger in diameter toward the median sector. Rhizoids typically on stoloniform axes, usually originating from cells of underleaves and, sporadically, leaves, rarely near bases of leafy shoots. Leaves often falcate, often somewhat ventrally secund, asymmetric, bifid to 0.4–0.8 (rarely asymmetrically 3-fid in a few taxa), the lobes subequal or the dorsal slightly larger, the lobes narrowly acute-lanceolate to acuminate-lanceolate, entire; lamina margins entire or with several slime papillae and, at times, teeth terminating in a slime papilla. Cells with trigones strongly nodulose, often confluent, vittate: with a median-basal field of elongate-rectangular cells extending into the lobes (frequently to the lobe tips), the marginal and submarginal cells ± isodiametric; surface striate-papillose. Oil-bodies up to 20–24 per vitta cell, glistening, homogeneous, smooth. Underleaves at times slightly smaller than leaves, transversely inserted, symmetric, typically ± squarrose, not falcate, the lobes ± parallel to slightly divergent.
Dioecious. Androecia wider than sterile sectors of shoot, typically with 4–8 pairs of bracts, subspicate; bracts and bracteoles similar to leaves and underleaves in form but pouched at the base, typically less deeply bifid and with lamina margins more toothed, both bracts and bracteoles with 2–3 antheridia. Gynoecia with bracts and bracteoles in 3–4 series, the innermost series much larger than leaves, deeply bifid, the lamina margins (and at times the basal sector of the lobes) denticulate-dentate. Perianth plicate, the mouth divided to 0.3–0.5 into 6 lobes similar to those of the leaves, with each alternate sinus somewhat more deeply descending; lobe margins (and at times also the inner surface) often dentate, with numerous slime papillae.
Seta of numerous cells. Capsule subspherical, with 4 valves, but occasionally with secondary, irregular splitting into additional valves, the wall 5–9-layered.
Spores with truncated tubercles, ca. 2–2.5× the elaters in diam. Elaters 2–3-spiraled.
Herbertus has ca. 25 species (Gradstein et al., 2001) and is widespread in montane, subalpine and alpine regions. A few species occur in the Northern Hemisphere, e.g., western Europe, Appalachia, western North America (including Arctic Alaska), but the genus is more predominantly in tropical regions. Ten species, for example, occur in tropical America (Gradstein et al., 2001), and eight species occur in Australasia and the South Pacific (So, 2003b). The genus is not well represented in southern temperate and subantarctic regions. One species, H. runcinatus (Taylor) Kuntze, is found in southern South America and Juan Fernandez (Hässel and Solari, 1976; Engel, 1978), and one occurs in New Zealand and Tasmania.
References: Hodgson (1967; H. alpina); So (2003b); Stewart (1978; oil-body data of H. alpina; Schuster, 2000a).
