Diplazium thailandicum Pongkai, Boonkerd & Pollawatn (2018: 227)

Pongkai, Puttamon, Zhang, Li-Bing, Boonkerd, Thaweesakdi & Pollawatn, Rossarin, 2023, Revision of the fern genus Diplazium (Polypodiales: Athyriaceae) in Thailand, Phytotaxa 631 (1), pp. 1-69 : 61-64

29. Diplazium thailandicum Pongkai, Boonkerd & Pollawatn (2018: 227) . Fig. 35 , 36 .

Type : THAILAND. P . Pongkai 107 (holotype BCU!) .

Plants terrestrial. Stem creeping, 0.5–1.0 cm diameter, densely corvered with scales; scales 8–10 × 1–2 mm, linear lanceolate with long tail apex, concolorous, dark brown to nearly black, denticulate and thick at margin. Fronds 72–93 cm, monomorphic, imparipinnate; petioles 29-47 cm, 3–5 mm in diameter, deep green when living, brown when dried, black and scaly at base, groove above. Laminae 43–50 × 23–33 cm, ovate to lanceolate-oblong in outline, papyraceous; rachises groove, glabrous; pinnae 5–8 pairs, subopposite to alternate, terminal pinna distinct, different form lateral pinnae; terminal pinna 17–19 ×3.5–8.0 cm, narrowly ovate in outline with usually slightly pinnatisect at base, widest at base, apex long acuminate, base obtuse to subtruncate, margin subentire to slightly lobe; largest lobe 2.0–4.5 × 1.0– 1.5 cm, lanceolate, apex acute to acuminate, margin subentire; lateral pinnae 14–22 × 2.5–3.0 cm, oblong, apex long acuminate, base obtuse to subtruncate sometimes slightly oblique, margin subentire to shallowly lobed, serrate near apex, stalked; stalk 2–4 mm; vein all free, veinlets 3–4 pairs, pinnate, reaching margin. Sori curved, elongate along veinlet, 0.5–0.7 cm, half way between midrib and margin, usually on acroscopic veinlet of each vein group, close to midrib, indusiate; indusia linear, thin, persistence; spores monolete, bilateral symmetric, kidney-shaped, 61.5–63.0 × 31–32 μm, perispore present; ornamentation: prominent wing folds.

Thailand: —NORTHERN: Chiang Rai (Me Lao), Chiang Mai (Doi Suthep), Nakhon Sawan (Doi Musae), Phitsanulok (Mun Daeng Waterfalls), Phitsanulok (Phu Hin Rong Kla National Park), Petchaburi ( Kaeng Krachan National Park ).

Distribution: — Thailand.

Ecology: —On shady valleys at an elevation ranging from 570–1,700 m.

Specimens Examined:— THAILAND. Chiang Rai, Me Lao, Winit 958 (K); Chiang Mai, Doi Suthep, M. Tagawa & N. Kitagawa T3859 (K); Nakhon Sawan, Doi Musae, E. Hennipman 3056 (L); Phitsanulok, Mun Daeng Waterfalls, P. Pongkai 110 (BCU); ibis., Pteridophyte trip 72 (BCU); ibis., W. Rattanathirakul 29, 106 (BCU); Petchaburi, Kaeng Krachan National Park, K. Williams 1130 (L).

Note: —This species is also similar to the recently describe species, Diplazium yinchanianum Zi Y. Liu, H.J. Wei & Y.H. Yan (2018: 143) in having creeping rhizome, once-pinnate frond and scales with denticulate and thick margins, but differs in having oblong pinnae with obtuse to subtruncate or slightly oblique base and subentire margins, stalk <4 mm, and sori usually borne on acroscopic veinlet of each vein group. In contrast, D. yinchanianum has pinnae with oblong-lanceolate or sickle-shaped lanceolate, rounded or shallowly cordate base, and dentate margins, stalk> 4 mm, and sori borne on all veinlets of each vein group.

Figures

FIGURE 35. Diplazium thailandicum Pongkai, Boonkerd & Pollawatn. A, whole plant. B-C, pinna with sori. D, scale showing toothed and black marginal cells. P. Pongkai 107 (BCU).

FIGURE 36. Diplazium sylvaticum (Bory) Sw. A, living plant. B, rhizome. C, sori. D, scale. E, SEM spore.