Lembidium nutans (Hook.f. & Taylor) Mitt.
Jungermannia nutans Hook.f. & Taylor, London J. Bot. 3: 389. 1844.
Mastigobryum nutans (Hook.f. & Taylor) Gottsche, Lindenb. & Nees, Syn. Hepat. 219. 1845.
Micropterygium nutans (Hook.f. & Taylor) Mitt. in Hook.f., Bot. Antarc. Voy. 2: 148. 1854.
Bazzania nutans (Hook.f. & Taylor) Trevis., Mem. Reale Ist. Lombardo Sci. Lett. III, 4: 414. 1877.
Cephalozia nutans (Hook.f. & Taylor) Spruce, Cephalozia 97. 1882.
Type: Auckland Is., Hooker (G!).
Plants pale, whitish green, water-repellent, quite opaque when dry, when wet becoming pellucid; leafy shoots 1.1–1.6 mm wide × 7–12 mm high, often circinate or hamate. Leafy branches sporadic to rather common, the branches mostly terminal, of the Frullania type and 1(2) per leafy shoot, or sporadically ventral-intercalary. Stems of leafy shoots fleshy, of leptodermous cells throughout, quite pellucid, virtually echlorophyllose, the epidermal cells with diffuse chloroplasts; cortical cells strongly elongated, narrowly oblong; lateral merophytes formed of 2–3 tiers of cortical cells. Leaves contiguous to distinctly imbricate, inflated in aspect, not folded-canaliculate and without a discernible “keel” between halves of the leaf, broadly ovate to ovate-rotund when flattened, the insertion transverse to weakly incubous; apices undivided and entire to emarginate or bidentate or quadridentate; margins entire or crenulate through projecting cells, or occasionally with an isolated tooth terminating in a slime papilla; leaves with a distinct basal area of much larger, more inflated, pellucid cells, the peripheral cells relatively small. Cells bulging or strongly convex in leaf profile, rather small, 16–22 × 20–26 µm, in the area basalis becoming pellucid, swollen and very large, from a minimum of 25–30 × 70 µm to 45–60 × 80–120 µm; cells very slightly chlorophyllose, the cells of the area basalis hardly so; surface of area basalis cells smooth or striolate, the surface of peripheral cells and elsewhere papillose. Oil-droplets present in some populations, tiny, homogeneous. Underleaves ± imbricate, transversely inserted, ovate to rotund-ovate; apices crenulate-denticulate to shallowly bilobed; disc margins entire. Fungal partner absent.
Gynoecia with innermost bracts lanceolate to narrowly ovate-lanceolate from a broad, truncate base, large-celled, hyaline, thin, tapered to a narrow, pointed or bidenticulate tip; upper margins and apex ± crenulate marginally with free ends of elongated cells, otherwise entire. Perianth tapering in the distal 0.35–0.4 to a conical, almost pointed tip, the perianth formed of exceedingly large, thin-walled, oblong cells; mouth cells from 55–60 × 13–17 µm to 80 × 13 µm.
Sporophyte details in the generic description above.
Distribution and Ecology : Endemic to New Zealand: Campbell Island, Auckland Islands, Stewart Island (10–530 m), South Island (10–1140 m), North Island (170–1100 m). Known from Fiordland, Otago, Westland, Canterbury, Western Nelson, Southern North Island, Taranaki, Gisborne, Volcanic Plateau, Auckland and Northland EPs.
Unlike Lembidium longifolium, which inhabits only very sheltered sites, L. nutans tends to be a pioneer (particularly over clayey soil) on relatively well-illuminated banks, paths and road cuts, where sporadic desiccation occurs. The extensive system of subterranean rhizoidous axes may be of significance in consolidating roadside and trackside banks, a characteristic habitat of the species. The species at times may occur in sheltered niches, but these differ from those characteristic of L. longifolium. For example, L. nutans occurred on the ventral-lateral side of a rotted, decorticated log in a wet mossy forest of Lepidothamnus intermedius, Ixerba brexioides and Dacrydium cupressinum with occasional Phyllocladus glaucus (summit of Table Mtn., Coromandel Forest Park, 835 m). Also forming a solid patch in a mound of Balantiopsis tumida at the edge of a narrow, shallow, stagnant pool with saturated, rich, peaty soil in a mixed podocarp–broadleaf forest, the vegetation consisting of Dacrydium cupressinum, Weinmannia racemosa and Podocarpus totara, with an open understory dominated by Pseudowintera colorata (Lake Kaniere Scenic Reserve, Westland, 125 m). In the penalpine zone on soil banks under Olearia colensoi scrub and Chionochloa pallens tussockland. Accompanying species are Balantiopsis diplophylla, Distichophyllum pulchellum, D. rotundifolium, Ditrichum difficile, Fissidens pallidus, Hygrolembidium australe, Lepidozia pendulina, Leucobryum candidum, Pallavicinia xiphoides, Riccardia colensoi, R. crassa, Sticta filix and Telaranea lindenbergii.
Comments : Lembidium nutans is a most peculiar plant. The erect, often crowded, pale to whitish green leafy shoots are quite distinctive, with their contiguous-imbricate, hollowed-out, distichous leaves. These shoots are always of very limited and finite height and arise from a system of whitish, flagelliform axes that may penetrate the substrate for 2–3 cm, if not more. The plant does not have the facies of a member of the Lepidoziaceae, although the occasional occurrence of a terminal, Frullania -type branch, associated with the ventral, long stolons and the restricted rhizoids are “lepidozioid” features. The total lack of oil-bodies is notable. Unlike L. longifolium, which has more flattened shoots with weakly decurved tips, L. nutans has diagnostically cernuous shoot apices, as the species name suggests. Most similar in appearance to Chloranthelia berggrenii and the two may be found in similar habitats, but L. nutans lacks the obvious teeth on the leaf margins of that species. Similar to Hygrolembidium acrocladum and H. australe, which occur in similar habitats, but the leaves of L. nutans are opaque, whereas those two species have translucent leaves.
