Isachne dimyloides Bor (1949: 96)

Devi, Moonmee & Bhattacharyya, Debjyoti, 2015, Rediscovery of the red-listed grass Isachne dimyloides (Poaceae: Micrairoideae) 130 years after type collection, Phytotaxa 221 (1), pp. 93-96 : 93-94

Isachne dimyloides Bor (1949: 96) . ( Fig. 2 )

Type: — INDIA. West Bengal, Darjeeling district, ‘ Sikkim Terai’, Dulkajhar , 500 ft, 16 October 1884, C. B. Clarke 36764 [holotype K, digitized image! ( K000245438 ); isotypes CAL, original specimen! ( CAL0000002103 ) & BM, digitized image! (000573595 BM)] .

Description: —Annuals, creeping. Culms decumbent, erect, 7–30 cm high, greenish; nodes pubescent with lower nodes rooted; internodes 1.3–3.4 cm, ribbed, glabrous. Leaf blades lanceolate, 1.5–4.5 × 0.4–1.1 cm, acute, glabrous; margins cartilaginous, thickened, whitish; midrib prominent abaxially. Leaf sheaths shorter than the internodes, ribbed, glabrous; ciliate at both margins; cilia with long tubercled bases. Ligule ca. 2 mm long, erect, whitish hairy. Panicle pyramidal, 1.6–4 × 1–3.3 cm, few flowered; raceme branches 0.3–1.3 cm long, ascending; peduncle ribbed, glabrous, eglandular. Spikelets morphologically alike, subglobose to obovate, 1.8–2.6 × ca. 1 mm, acute, greenish-yellow, pedicellate; pedicels sparsely scabrous. Glumes subequal, ovate, 1.8–2.5 × 1 mm, as long as the spikelets, acute, 9–11 nerved, pubescent in between nerves on abaxial surface. Lower glume narrower than the upper one, membranous along margins; glumes persistent or sometimes deciduous. Florets 2, disarticulating above glumes; lower hermaphrodite, upper female; both of same shape and texture, coriaceous, flattened on the back; upper floret slightly shorter than lower, stipitate. Lower lemma subglobose, 1.5–1.8 × ca. 1 mm, obtuse, rolled at margins, glabrous to minutely pubescent along margins on abaxial surface. Upper and lower lemmas 1.3–1.5 × ca. 1 mm. Lower palea 1.2–1.5 × ca. 0.9 mm, depressed longitudinally at middle, 2-nerved, minutely pubescent on abaxial surface. Palea 1.1–1.3 × ca. 0.85 mm. Lodicules 2, ca. 0.2 mm, cuneate at base, glabrous, hyaline. Stamens 3; anthers ca. 1 mm long. Ovary ovate-oblong, ca. 0.4 mm long, glabrous; style 2, glabrous; stigma 2, plumose.

Flowering & Fruiting:—March–October.

Habitat:—Shady, moist marsh along the bank of a ditch/stream in association with Isachne miliacea Roth ex Roem. & Schult. in Roemer & Schultes (1817: 476), Panicum laxum Swartz (1788: 23) , and others.

Distribution:— India: West Bengal (Darjeeling district); Assam (present report), Endemic.

Additional specimen examined:— INDIA: Assam, Barak Valley, Cachar district, Loharbond, Innerline Reserve Forest, 33 m, 25 March 2012, M. Devi & D. Bhattacharyya 10877 (ASSAM, CAL, Herbarium of Department of Life Science & Bioinformatics, Assam University-Silchar, Assam, India).

Notes:—The present collection was made from a moist, shady forest area near a small stream. The population of this species inhabiting the forest was found to be disturbed due to the establishment of a bambusetum in the area. The authors could locate only one population of this species in the study area. IUCN red-listed this endemic species as a threatened taxon of India in 1997 ( Rao et al. 2003). The species should be prioritized for in situ and ex situ conservations to maintain the genepool of this rare and endemic taxon. In the collection site of this species, Isachne miliacea also occurs.

Figures

FIGURE 2. Isachne dimyloides. A. Habit. B. Spikelet. C. Adaxial view of lower glume. D.Abaxial view of lower glume. E.Adaxial view of upper glume. F. Abaxial view of upper glume. G. Adaxial view of lower lemma. H. Abaxial view of lower lemma. I. Adaxial view of lower palea. J. Abaxial view of lower palea. K. Adaxial view of upper lemma. L.Abaxial view of upper lemma. M.Adaxial view of upper palea. N. Abaxial view of upper palea. O. Lodicules. P. Stamens. Q. Pistil. Drawn from M. Devi & D. Bhattacharyya 10877. Drawn by M. Devi.