Radula strangulata Hook. fil. & Taylor

[From CHR579214] Forming interwoven mats of shoots, glaucous yellow-green to brown-green in life, brown in herbarium; shoot systems regularly pinnately branched in male plants and sterile female plants, but pseudodichotomous in fertile female plants due to production of pairs of subfloral innovations below gynoecia, monomorphic, 1.0–2.0 mm wide and up to 40 mm long, branches initially smaller in stature than parent shoot and attaining similar stature by third to fifth pair of leaves; older shoot sectors retaining leaf-lobes. Stems 115–175 µm diameter, with cortical cells in a single tier of 16–25 rows, cell walls yellow-brown to brown pigmented, external free cortical cell wall heavily and continuously thickened, radial longitudinal walls thin, inner tangential walls thin or continuously thickened; medulla cells in 18–35 rows, cell walls yellow-brown pigmented, sometimes deepening to brown pigmented on old shoot sectors, cell walls with small triangular trigones, walls between trigones lacking thickenings. Cortical cells on dorsal stem surface arranged in straight longitudinal rows on young and mature shoot sectors. Leaf insertion not reaching dorsal stem mid-line, leaving four or five dorsal cortical cell rows leaf-free; leaf insertion not attaining the ventral stem mid-line, leaving two or three ventral cortical cell rows leaf-free. Leaf lobes elliptic-ovate, 550–1050 µm long by 400–830 μm wide, remote to contiguous, not falcate, acroscopic base not sharply deflexed away from stem, flat, lying in plane with stem, not interlocking over the dorsal stem surface, stem visible between leaf lobes in dorsal view; margins irregularly but minutely repand, minutely crenulate, the interior lobe margin not or at most shallowly ampliate, hardly covering the dorsal stem surface and not reaching the opposite stem margin, antical margin curved, exterior margin curved through nearly 100°, postical margin straight; angle between postical lobe margin and keel c. 135°. Lobules quadrate when small to oblong, one twelfth to one sixth the lobe area, 270–490 µm long by 140–270 μm wide; keel straight to shallowly arched, angle between keel and stem 135–150°, keel turning through 90° at keel-lobe junction, keel apex and postical lobe margin flush; interior lobule margin free for one fifth to one quarter its length, free portion not ampliate in small stature lobules to moderately ampliate on large lobules, extending at most half way across the ventral stem surface; acroscopic margin S-shaped, apical portion perpendicular to stem; apex obtuse to apiculate; free exterior margin straight, margins plane, crenulated; lobe-lobule junction well postical to the acroscopic end of stem insertion; attached to stem along 0.75 to 0.8 of the interior margin, stem insertion more or less straight, not curved at acroscopic or basiscopic ends, not revolute; lobule apex bearing a single papilla, with another two papilla situated on the interior lobule margin above the stem insertion. Leaf lobe cells rounded-oblong, not arranged in rows, unequally sized, 10–25 µm long by 9–19 μm wide, thin walled with small triangular trigones, medial wall thickenings absent; cells of lobe margin smaller than those of leaf middle, quadrate to rectangular, 9–15 µm long and wide, interior and exterior cell walls not differential thickened, cell lumen bulging medially; leaf lobe cell surface unornamented, smooth. Oil-bodies two or three per cell, ellipsoidal, filling cell lumen, light-brown, surface granular, internally homogeneous or with a hyaline droplet. Asexual reproduction usually absent, however two specimens have been observed producing bud-like shoot primordia from leaf lobe margins. Dioicous. Androecia on indeterminate branches that continue vegetative or reproductive growth, androecial bracts in 4-∞ pairs, lobules epistatic, keel deeply curved, bucket-like, free apical portion triangular, apex obtuse, moderately deflexed, lobes rounded, not caducous, antheridia not seen. Gynoecia terminal on leading shoots, subtended by two full subfloral innovations that are usually full-sized and again fertile; archegonia 130–155 µm tall, archegonia neck five or six cell columns, 6–8 per gynoecium on a small disc of tissue, not encompassed by the protoperianth; female bracts in one pair, slightly asymmetrical, tightly imbricate, elliptic-ovate, weakly falcate, lobe 840–1015 μm long by 460–545 μm wide, margins entire; lobules rhomboid to trullate, one quarter to one half the lobe area, apex acute to acuminate, keel straight to arched, margins entire; bract insertion lines interlocking dorsally and ventrally, insertion equitant. Perianths 3200–3800 µm long and 840–980 µm at mouth, mouth entire to irregularly lobed, perianth shape variable, either broadening from mouth to widest point at approximately one third to one half length above base, where 850–950 µm wide, then tapering to base, or tapering from mouth to base; perianth walls unistratose above, with bistratose collar 3 or 4 cell tiers high above the perianth-calyptra junction; long stem perigynium present, 5-6 stratose, cell walls not thickened or pigmented, perianth-calyptra fusion elevated above female bracts on 9–15 tiers of cells; calyptral perigynium present, base of calyptra bistratose, unistratose above, unfertilised archegonia elevated on surface of calyptra.

Radula strangulata is widely distributed throughout the New Zealand Botanical Region, from the Kermadec Islands in the north, throughout the North, South, and Stewart Islands, south to the Auckland and Campbell Islands, and east to the Chatham Islands. Radula strangulata occupies an elevational range from sea level to c. 800 mencompassing lowland to montane habitats, including coastal scrub, mature and regenerating lowland podocarp-broadleaf forest and beech forest on both sides of the main axial ranges in North and South Islands. Radula strangulata also has a broad ecological amplitude, occupying a range of microsites from tree trunks and bases, exposed tree roots on the forest floor, to rotting logs, exposed clay on forest banks, dripping rocks adjacent to waterfalls, and on rocks within stream beds, sometimes under running water. In hyperhumid locations Radula strangulata may grow epiphyllously on fern fronds. This is the only Radula species in New Zealand commonly encountered growing aquatically, typically submerged on basaltic boulders within cool, clear, fast flowing streams. It is also the only Radula species encountered in suburban areas where it is opportunistic in a range of man-made habitats in suitably moist sites, for instance the surfaces of rotting wooden roof tiles. Radula strangulata is the most commonly collected species of Radula in New Zealand, and despite this accessibility bias, is probably the most common species of Radula in New Zealand. When growing on naked bark Radula strangulata forms tightly adherent mats, and usually grows admixed with Radula allisonii. Radula strangulata also grows in epiphytic turfs with Radula plicata, Radula demissa, Archilejeunea olivacea, various Cheilolejeunea species, Plagiochila spp. In terrestrial habitats and on rotting logs, Radula strangulata occurs with a wide variety of bryophytes, including the mosses Pendulothecium punctatum, Echinodium umbrosum, Catharomnion ciliatum, Fissidens tenellus var. australiensis, and the liverworts Heteroscyphus spp., Chiloscyphus spp., Saccogynidium and many other species. On rocks and tree roots on the forest floor with Pendulothecium oblongifolium, Pendulothecium punctatum, Acromastigum colensoanum, Chiloscyphus muricatus, Radula marginata.