Adelanthus occlusus (Hook.f. & Taylor) Carrington
Jungermannia occlusa Hook.f. & Taylor, London J. Bot. 3: 369. 1844.
Alicularia occlusa (Hook.f. & Taylor) Gottsche, Lindenb. & Nees, Syn. Hepat. 619. 1846.
Adelanthus occlusus (Hook.f. & Taylor) Carrington, Trans. Bot. Soc. Edinburgh 10: 381. 1870.
Odontoschisma occlusum (Hook.f. & Taylor) Trevis., Mem. Reale Ist. Lombardo Sci. Lett. III, 4: 419. 1877.
Jamesoniella occlusa (Hook.f. & Taylor) Steph., Sp. Hepat. 2: 102. 1901.
Calyptrocolea occlusa (Hook.f. & Taylor) R.M.Schust., Rev. Bryol. Lichénol. 34: 692. 1967 (1966).
Type: Campbell Is., Hooker.
[Fig. 134; Fig. 146: 2, oil-bodies, p. 672]
Plants erect, caespitose, similar to Adelanthus falcatus but a little larger, the leafy shoots stiffly erect, simple or rarely branched, the shoots at most weakly cernuous at the extreme tips, the leaves similar in size and form above (except when gemmae are produced), the stems brown to fuscous but not black (except with decay), the leafy shoots to 5(6) cm tall. Branching all intercalary; leafy shoots arising from lowermost sectors of earlier generations of leafy shoots, from their leafless bases, or from stoloniferous axes and/or geotropic axes. Stems with cortex (1)2(3)-stratose, of very thick-walled, oblong to narrow-oblong cells. Leaves erect or suberect to appressed laterally to stem, vertically or subvertically oriented, decurved-homomallous, contiguous to (in lateral aspect) imbricate, the insertion nearly transverse in dorsal half, almost flat apart from a ± concave basal region, asymmetrically broadly reniform, broader than long, the ventral “half” extraordinarily ampliate, ± auriculate at base, the leaves strongly constricted to the narrow base, 1425–1500 µm wide × 925–950(1120) µm long to 1825 µm wide × 1140 µm long, the margins usually completely entire, rare and sporadic leaves with a few isolated small teeth, especially on distal leaves. Cells oriented in very regular lines, radiating fan-like from the contracted base, the cells very small and thick-walled in peripheral and apical sectors, 13–23 µm wide and long, gradually decreasing to 12–15 × 16–24 µm medially; basal cells forming a field of strongly elongated cells, 15–21 µm wide × 36–48(60) µm long to 13–16 µm wide × (38)40–54(66) µm long (3–3.5:1), with the longitudinal walls thick and often sinuous; surface smooth. Oil-bodies occupying a conspicuous portion of the cell lumen, dull opaque, with a cloudy appearance, 3–6(7) per median leaf cell, obscurely and irregularly botryoidal, the spherules protruding beyond the membrane. Underleaves lacking. Asexual reproduction via gemmae, these only at tips of leafy shoots, 2-celled, ellipsoidal, green, 13–14 × 18–23 µm to 15–16 × 18–21 µm and somewhat thick-walled.
Androecia unknown. Gynoecia on ventral, slight basitonic branches; bracts small, hyaline, the inner ovate, bilobed, the lobes crenulate-denticulate; shoot-calyptra fleshy, cylindrical-clavate, 2.2–2.4 mm long, 700–725 µm in diam., with unfertilized archegonia chiefly in basal 0.2–0.25. Perianth totally lacking.
Capsule ovoid, the wall 38–42 µm thick, of 4–5 layers; outer layer of cells with alternating (secondary) longitudinal walls with strong nodular thickenings; intermediate layers with strong nodular (radial) bands somewhat or strongly tangentially extended; innermost layer with strong, complete to incomplete semiannular bands, often complete also on internal walls (annular).
Spores 13.5–15.5 µm in diam., brown, the spore wall bearing low, delicate, simple or sometimes furcate vermiculate markings that usually fail to anastomose. Elaters 8–8.5 µm in diam., moderately attenuate at ends, bispiral, the spirals 3 µm thick.
Distribution and Ecology : New Zealand: Campbell Island (70–310 m), Auckland Islands (70–560 m), Antipodes Islands (150–400 m), Stewart Island (500–1000 m), South Island (760–1200 m), North Island (760–1320 m); Australia: Macquarie Island, Tasmania, Western Australia. In New Zealand known from Fiordland, Westland, Western Nelson, Volcanic Plateau, Gisborne and Auckland EPs.
A species with a scattered and sporadic distribution but most abundant on the subantarctic islands. It occurs in Nothofagus menziesii and N. solandri var. cliffortioides forests, at times in masses of bryophytes over rotted wood or on steep, moist, peaty, mossy banks. Also on wet, peat-covered ledges or cliff faces, often where kept moist by seepage. On the Thousand Acres Plateau in the Matiri Ra. (Kahurangi Natl. Park, Western Nelson EP) occurring at ca. 1100–1200 m on the bank of a small still pool in a mosaic of Chionochloa rubra tussocklands, shrublands, Phormium cookianum tussocklands and Celmisia monroi herbfields. At the summit area of Te Rangaakapua (Huiarau Ra., Urewera Natl. Park) it occurred at 1265–1320 m on a nearly vertical bank at the margin of a wet depression in a mosaic of stunted Olearia colensoi and tussock with occasional Coprosma spp. At Mt. Moehau (summit area of “Little Moehau”) it was found at ca. 850 m on a rock face of a large rocky outcrop in an area of very exposed bedrock with tufts of vegetation in protected pockets and crevices with windswept, dense scrub at the base, including Leptospermum scoparium, Dracophyllum recurvum and Phyllocladus alpinus. On Stewart Island occurring in a protected pocket with Anastrophyllum schismoides in mosaic communities of dense heath-forming shrubs to 3 m tall, penalpine herbs and dwarf heaths to 0.5 m tall, dominated by stunted L. scoparium and Dracophyllum and a ground tier including Empodisma minus (Mt. Rocky summit, 530 m). Also growing erect in a cushion of flowering plants in mosaic communities consisting of penalpine cushion vegetation, prostrate L. scoparium and Olearia colensoi to 1 m tall (Mt. Rakeahua, 500 m). Found with Acromastigum anisostomum, Bazzania nitida, B. involuta, Chiloscyphus leucophyllus, C. spiniferus, Clandarium xiphophyllum, Dicranoloma billardierei, D. robustum, Eotrichocolea polyacantha, Gackstroemia alpina, Herbertus oldfieldianus, Heteroscyphus decipiens, Lepidozia hirta, L. ornata, Marsupidium surculosum, Ptychomnion aciculare, Racomitrium crispulum, Schistochila monticola and Temnoma quadripartitum.
Comments : A distinctive species that should not be confused with Adelanthus falcatus. Unlike A. falcatus, leaves are essentially entire-margined (Fig. 134: 1–4) and the shoot tips are never strongly coiled (Fig. 134: 1, 2); the uppermost leaves are reduced only when gemmae are produced.
Plants of Adelanthus occlusus have a Plagiochila -like appearance, and indeed closely mimic Plagiochila retrospectans, which may be very similar when it has subentire or minutely denticulate leaves. Weak forms of P. retrospectans and A. occlusus have a very similar facies, with leaves that are similar in shape. The leaves of these two species both have a border of small, thick-walled, subisodiametric cells, and a basal area of narrow, elongate cells. However, the subapical and median cells in P. retrospectans have very coarse, usually nodose trigones, and the dorsal leaf margins are somewhat deflexed, as in other Plagiochila species. In A. occlusus the dorsal margins are narrowly infolded or inflexed, as is normal for most Adelanthaceae. Also, the presence of gametangia, even when young, will immediately separate the Plagiochila on position of sex organs alone.
The erect, asymmetrically reniform leaves have a cell arrangement that is highly distinctive: the basal cells form an area of strongly elongated cells (3–3.5:1), with the longitudinal walls thick and often sinuous (Fig. 134: 7), grading into rectangular cells and then into submarginal and marginal cells that are more nearly quadrate and thicker-walled (Fig. 134: 5). Thus, the cells tend to be oriented in very regular lines, radiating fan-like from the contracted base (Fig. 134: 5).
Grolle (1972a) placed Plagiochila orbiculata Colenso in the synonymy of Adelanthus occlusus, but did not see the type. One of us (JJE) has seen the type specimen of P. orbiculata in the Geneva herbarium; it is Plagiochila gigantea (see also Inoue and Schuster, 1971, p. 190).
