Diplophyllum dioicum R.M.Schust.
Diplophyllum dioicum R.M.Schust., Bull. Natl. Sci. Mus. Tokyo 11: 20. 1968.
Holotype: New Zealand, South Is., Fiordland Natl. Park, track from Lake Mackenzie to Harris Saddle, Humboldt Mtns., 3800–4000 ft., Schuster 67-386c (F).
Plants rigid, brittle, loosely creeping to ascending, dark green to yellowish brown, without reddish pigmentation even in sun forms; shoots strongly dorsiventrally compressed, with the ventral lobes ± plane, the shoots medium, to 2 mm wide. Branches sparingly developed to frequent, lateral-intercalary. Rhizoids when present scattered on ventral face of stem. Stem stout for plant size, the cortex in 2–4 layers of smaller, thick-walled, yellow-brown cells, the outer layer especially thick-walled. Leaves stiff, contiguous to imbricate, regularly arranged, ladder-like, conduplicate-bilobed, the dorsal lobe ± appressed to the ventral; leaves somewhat dorsally assurgent when dry, when moist horizontal to slightly decurved, widely spreading to squarrose, often distinctly falcate, the keel 0.25–0.35 the leaf length, strongly arched, the sinus abruptly reflexed and sometimes flaring, the opposing dorsal lobes (when leaves imbricate) overlapping, extending to 0.5 the stem width or a little more. Ventral lobe plane or decurved at the tip, the insertion ± transverse, the free margin contracted and subcordate at the base, not decurrent, the lobe elliptic-oblong, lingulate, abruptly contracted at the keel; apex broadly rounded to subtruncate or at times subacute, denticulate, sporadically with a minute, single-celled apiculus; ventral margin broadly and ± symmetrically arched, finely and regularly to somewhat irregularly denticulate (rarely subentire), at times ± repand, the teeth larger near the base; dorsal margin rarely subentire. Dorsal lobe plane, ± appressed to the ventral, asymmetrically ovate to elliptic, 0.65–0.8 the length of ventral, 0.45–0.65 the area of ventral lobe, the insertion ± transverse, not decurrent; apex broadly rounded or at times subacute, sometimes with a minute apiculus similar to that of ventral lobe; dorsal (free) margin ± broadly arched, often contracted at the base, with denticulation similar to that of ventral lobe, but less strongly toothed at the base. Marginal teeth unicellular, consisting of sharp projections of the exposed marginal cell walls, the margins near the lobe bases more sharply toothed (especially the ventral, where sharply spinulose-denticulate). Cells of median portion of ventral lobe ± isodiametric, subquadrate to short-rectangular, 10–14 µm wide × 14–17 µm long; subapical and marginal cells uniformly moderately to distinctly thick-walled, in ± regular arching tiers in distal 0.3 of lobe, 9–13 µm wide and long; basal cells of ventral lobe and keelar region elongate-rectangular, much larger than median cells of lobes, 12–16 µm wide × 35–60 µm long, forming a distinct, sharply delimited vitta equaling the keel in length and ending ± abruptly distally, the longitudinal walls of the vitta cells thickened and sinuous, the transverse walls thin; surface conspicuously and coarsely papillose, the papillae rounded to elliptic, 2–5 per cell; vitta cells finely striolate-papillose. Oil-bodies (Schuster, 1968a) (1)2–5(7) per cell, almost homogeneous in appearance, smooth, colorless, spherical and subspherical, 3–3.5 × 3–4 µm to 5.5–6.5 µm, often ellipsoidal, 4–5 × 5–6.5(7.5) µm. Gemmae almost colorless, 1–2-celled, polygonal, 12 × 14–17 µm to 13 × 13–15 µm.
Dioecious (presumably, but androecia not seen). Gynoecia with 1–3 subfloral innovations; subgynoecial leaves somewhat larger than vegetative leaves but considerably more coarsely armed, those of inner series smaller, deeply concave, shallowly 2–3-lobed. Perianth ovoid to somewhat compressed, strongly and deeply pluriplicate toward the moderately contracted mouth, the mouth decolorate, closely spinulose-denticulate with mostly 1-celled teeth formed of sharply tapered cells, the cells 9–10 × 18–26 µm.
Sporophyte not seen.
Distribution and Ecology : New Zealand: South Island (1000–1830 m); Australia: Tasmania (1200–1490 m). In New Zealand known from Fiordland, Otago, Westland, Canterbury and Western Nelson EPs.
A penalpine–alpine species occurring deep in shaded niches between boulders or over thin soil of damp ledges of rocky outcrops. The species has been found with Distichium capillaceum, Notoligotrichum australe, Pohlia wahlenbergii, Herzogobryum spp., Hygrolembidium acrocladum, Lepidozia obtusiloba and Andreaea. Near Kiwi Saddle (Western Nelson EP, 1100 m) it was found on a soil bank under Nothofagus menziesii and Dracophyllum longifolium forest mixed with Drucella integristipula. At Browning Pass (Canterbury, 1400 m) it was in Chionochloa oreophila – Marsippospermum gracile tussockland in a seepage, with Acrobolbus cinerascens, Cryptochila grandiflora, Dicranoloma robustum, Heteroscyphus billardierei, Metzgeria furcata and Pachyschistochila altissima.
Comments : Diplophyllum dioicum is a very distinctive species due to its strongly dorsiventrally flattened shoots (Fig. 166: 1, 10), regularly spaced, widely spreading, often distinctly falcate leaves, thickish stems (for the plant size) and deep green to yellowish brown color. In contrast to D. domesticum and D. novum, which have a rather indistinct field of short-rectangular cells extending to the middle of the ventral leaf lobe and sometimes beyond, D. dioicum has a distinct vitta, which is largely confined to the keelar region and extends laterally to about the middle of the ventral lobe base, and apically to just beyond the keel (Fig. 166: 4). The vitta also extends laterally into the dorsal lobe but is confined to the vicinity of the keel. The vitta cells are longer than in D. domesticum (to 39 µm long in D. domesticum vs. up to 60 µm long in D. dioicum) and the longitudinal walls are often distinctly sinuous-thickened. In D. dioicum the distal half of the leaf is uniformly densely areolate, composed of ± isodiametric cells.
This species is notable for its strongly dorsiventrally compressed shoots, so much so that it is sometimes difficult at first glance to distinguish the dorsal from the ventral side of the plant. The leaves are often distinctly falcate and are very regularly arranged in ladder-like fashion; the plant illustrated by Allison and Child (1975, p. 104) as D. domesticum is almost certainly D. dioicum judging from the aspect of the shoot, leaf shape and absence of ♂ bracts beneath the gynoecium. This species appears to be dioecious; only relatively young perianths have been seen and androecia are unknown.
