Thysananthus discretus Sukkharak & Gradstein (2010a: 113)

Sukkharak, Phiangphak, 2015, A systematic monograph of the genus Thysananthus (Lejeuneaceae, Marchantiophyta), Phytotaxa 193 (1), pp. 448-450 : 448-450

7. Thysananthus discretus Sukkharak & Gradstein (2010a: 113) . Type: INDONESIA. West Papua ["Netherlands New Guinea, distr. Hollandia"]: Cycloop Mountains, path Ifar-Ormoe , alt. 1220 m, 21 August 1961, van Royen & Sleumer 5896 (holotype L!; isotypes JE!, S!).

Plants dioicous, with projecting growth, turning upwards and becoming ascending to erect, with vigorous shoots, yellowish brown in herbarium specimens, up to 6.5 cm long × 2–3 mm wide. Stems strongly rigid; ventral merophyte 14–18 cell rows wide; stem in cross section orbicular-subelliptic, 360–500 µm high × 260–445 µm wide, 16–22 cell layers high, composed of 76–80 epidermal cells surrounding 365–381 medullary cells, epidermal cells as large as medullary cells. Leaves imbricate, when dry suberect and strongly convolute, when moist clasping the stem; dorsal lobe asymmetrically ovate, 1.4–2.3 × 1–1.8 mm, apex apiculate, dorsal base auriculate, auricle 100–150 × 125–160 µm, dorsal margin entire or with 1–4 triangular teeth, the teeth consisting of 3–4 cells, being 2–3 cells wide at base and ending in a row of 1–2 cells, ventral margin incurved over most of its length, becoming flat near the apex, entire or with 3–8 triangular teeth, the teeth consisting of 3–5 cells, being 2–3 cells wide at base and ending in a row of 1–2 cells; cells elongate-hexagonal with acute ends, vitta absent, marginal cells 10–12 × 10–12 µm, median cells 32–45 × 5–7 µm, basal cells 37–62 × 17–25 µm, trigones cordate, often coalesced, intermediate thickenings 0–1 per cell; oil bodies 4–5 per cell, toward leaf base more numerous, up to 8 per cell (Gradstein 3894). Lobules rectangular, 0.6–0.7 × 0.1–0.2 mm, 1/4–1/3 × lobe length; appendage on surface of lobule base not developed; keels with appendages on one or both sides or not developed, orbicular-oblong, 215–375 × 85–150 µm; lobule apex oblique, free margin continuing into the ventral lobe margin, apex with one triangular tooth, the tooth consisting of 5–12 cells, being 2–4 cells wide at base and ending in a row of 1–2 cells. Underleaves imbricate, slightly squarrose, broadly oblong to rectangular, 1.2–1.9 × 0.8–1.4 mm, ca. 3 × stem width, apex broadly rounded to truncate, plane, margin with 20–25 triangular teeth, the teeth consisting of 3–6 cells, being 2–3 cells wide at base and ending in a row of 1–2 cells, bases auriculate, auricles 100–275 × 200–400

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SUKKHARAK

µm, underleaf bases not adnate with leaves; cells 20–25 × 5–7 µm. Androecia terminal-intercalary on lateral branches, bracts, and bracteoles in 6–10 pairs, bracts hypostatic, 0.7–0.8 × 0.5–0.6 mm, apex acute, margins entire; antheridia 2 per bract. Gynoecia with 2 lejeuneoid innovations forming a dichasial pattern; lobe ovate, 2.4–2.7 × 1.2–1.5 mm, apex apiculate, margins in upper 1/3 with triangular teeth, the teeth consisting of 3–5 cells, being 2–3 cells wide at base and ending in a row of 1–2 cells; lobules broadly ovate, 2/3 × lobe length, apex apiculate, margin with triangular teeth, the teeth consisting of 3–5 cells, being 2–3 cells wide at base and ending in a row of 1–2 cells; bracteoles spathulate, 2.3–2.4 × 1.1–1.3 mm, apex emarginate, 1/2 × bracteole length with triangular teeth, the teeth consisting of 3–7 cells, being 2–3 cells wide at base and ending in a row of 1–2 cells, margins slightly recurved. Perianths oblong, 2.5–2.6 × 1.1–1.3 mm, keels in upper 1/3 with numerous laciniate teeth, the teeth consisting of 3–13 cells, being 2–3 cells wide at base and ending in a row of 3–9 cells; beak 97–125 µm (4–7 cells) in length. Fig. 16 .

Additional illustrations:— Gradstein et al. (2002, p. 73, Fig. 45, as Thysananthus convolutus ).

Distribution and ecology:— Endemic to Western Melanesia: Papua ( Indonesia), Papua New Guinea, and the Solomon Islands; 760–2700 m; on trunks, branches and stems of treelets in lowland rain forests (primary and secondary forests) and montane forests. Fig. 5O .

Representative specimens:— Indonesia. WESTERN NEW GUINEA: Papua, Cycloop Mts., van Royen & Sleumer 5907 (JE, L); Eipomek-Tal, Hiepko & Schultze-Motel 2218, 2403 (JE). Papua New Guinea. CENTRAL: Boridi, Carr 13531 (JE 2 packets).— EASTERN HIGHLANDS: Daulo Pass, Streimann 17990 (JE); Gahavisuka provincial park, Streimann 18201 (JE).— MOROBE: Wau, Mt. Kaindi, Gradstein 3778 (GOET, U), 3856, 3894, 3910 (U), Schuster 67–5786, 67–5787, 67–5791/c, 67–5792, 67–6282 (JE); Streimann 22497 (JE, LAE 2 packets), Streimann & Bellamy 17690 (BR, JE, S, W); Araulu logging area, Streimann 13622 (JE, LAE); Slate-Gumi creeks divide, Streimann 13861 (JE, LAE); Spreader divide, Streimann 26036 (JE), Streimann 11846 (LAE), Streimann & Tamba 11878 (JE, LAE); Aseki-Menyamya road, Streimann & Tamba 12156 (JE, LAE); Ekuti divide, Bulolo-Aseki road, Streimann 20051, 20103, 26135 (JE); Sattelberg, Clemens 265c (JE, L).— WESTERN HIGHLANDS: Jimi- Waghi divide, Streimann 20916 (JE, LAE), 20911 (LAE). Solomon Islands. GUADALCANAL: Mt. Papomanatsen, Braithwaite 4773 (JE).

Taxonomic notes:— Collections of Thysananthus discretus were previously identified as “ T. appendiculatus ”, “ T. convolutus ”, “ T. gottschei ”, and “ T. sp.”. Thysananthus discretus is most morphologically very similar to the widespread Malesian T. convolutus and was illustrated as T. convolutus by Gradstein et al. (2002: Fig. 45). The illustration clearly shows the free underleaves characteristic of T. discretus , which are not connected with the leaves, and the presence of well-developed auricles of the underleaf bases. Thysananthus discretus shares with T. convolutus the asymmetric leaves but differs from the latter by (1) leaves when moist clasping the stem (squarrose in T. convolutus ), (2) free underleaf bases, with well-developed auricles (underleaf bases adnate with leaves on one side and without auricles in T. convolutus ), and (3) strongly rigid stems, with 14–18 cells wide ventral merophytes and medulla 16–22 cell layers high (less rigid stems, with 8–10 cells wide ventral merophytes and 14–17 layers high medulla in T. convolutus ). Thysananthus discretus may also be confused with T. appendiculatus , a species endemic to New Guinea which may possess auricled underleaf bases like T. discretus . However, the leaf lobes in T. appendiculatus are symmetrical and widely spreading when moist, while in T. discretus they are asymmetrical and clasping the stem when moist. In addition, leaf and underleaf bases are connected in T. appendiculatus while in T. discretus they are never connected. In T. discretus the appendages are present on one or both sides of the stem and are sometimes lacking, while in T. appendiculatus , T. convolutus var. laceratus , and T. gottschei var. continuus they are always found on one side of the stem only, on leaves that are free from underleaf bases and opposite to leaves that are connected with underleaf bases. Moreover, the appendages of T. convolutus var. laceratus and T. gottschei var. continuus are always curved towards the stem while in T. discretus and T. appendiculatus they are straight or curved.

Thysananthus discretus is polymorphic with respect to the dentation of leaves, which vary from edentate to strongly dentate.

Figures

FIGURE 5. Distribution of Thysananthus species. A. Thysananthus amazonicus (Spruce) Schiffn. B. Thysananthus spathulistipus (Reinwardt, Blume & Nees) Lindenb. C. Thysananthus convolutus Lindenb. D. Thysananthus mollis Steph., E. Thysananthus pancheri (Steph.) Hürl. F. Thysananthus anguiformis (Hook.f. & Taylor) Taylor ex Gottsche, Lindenb. & Nees G. Thysananthus comosus Lindenb. H. Thysananthus fruticosus (Lindenb. & Gottsche) Schiffn. I. Thysananthus aculeatus Herzog. J. Thysananthus appendiculatus Steph. K. Thysananthus montanus Gradst., X.-L. He & Piippo. L. Thysananthus retusus (Reinw., Blume & Nees) B.M.Thiers & Gradst. M. Thysananthus gottschei (Jack & Steph.) Steph. N. Thysananthus ciliaris comb. nov. O. Thysananthus discretus Sukkharak & Gradst.

FIGURE 16. Thysananthus discretus Sukkharak & Gradst. A–B. Portion of shoot, ventral view. C–D. Leaves, ventral view. E–F. Underleaves, ventral view. G. Female bracts, ventral view: a appendage. H. Female bracteole, ventral view. I. Perianth, dorsal view. J. Perianth, ventral view. K. Leaf apex. L–M. Margin cells of leaf lobe. N. Median cells of leaf lobe. O. Basal cells of leaf lobe. P. Leaf lobule apices. Q. Cross section of stem. (A, C, E, G–K, M–Q from the holotype; B, D, F, L from Streimann 13622 (JE)).