Xyris emarginata Phonsena & Chantar., 2012

3. Xyris emarginata Phonsena & Chantar. View in CoL , sp. nov. — Fig. 3 View Fig , Plate 1f, g View Plate 1 , 2e, f View Plate 2 ; Map 1 View Map 1

Xyridi lobbii similissima bracteis fertilibus apice emarginato, sed margine lacerato non integro differt. Xyridi complanatae quoque similissima bracteae fertilis margine, sed ab ea folii aciebus et scapo laevi non tuberculoso differt. — Typus: Phonsena & Boonsuk 6585 (holo KKU; iso BK, BKF, C, K, L, QBG), Thailand, Bueng Kan, Bueng Khong Long, Pho Mak Khaeng, Ban Dong Chomphu , alt. 180 m, 25 Oct. 2010 .

Etymology. The specific epithet refers to the emarginate apex of the fertile bracts.

Caespitose perennial herb, 30–40(–45) cm tall, base dilated, bulbous. Bulb ovoid, 0.6 –1 by 0.4 –0.6 cm. Leave s 2 – 4 per plant, linear, twisted, 10 –20 cm by 1.5 – 2.2 mm, with a ligule; blade smooth, margin entire, apex bluntly oblique to acute. Scape terete, 1–1.5 mm thick, smooth. Spike ellipsoid, 0.8 –1.5 by 0.5 –1 cm. Sterile bracts 8 –12, reddish brown to brown, obovate, 3 – 6 by 2– 4 mm, margin entire. Fertile bracts reddish brown to brown, ovate, 7–8 by 4 – 5.5 mm, margin entire, apex emarginate; stomate field ovate, 2.5–3 by 1.2–2 mm. Lateral s epals pale brown, 7–8 by 1.5 – 2 mm, crest coarsely and distantly serrate. Petal limbs bright yellow, obovate, 8 –10 by 7–8 mm, margin fimbriate. Staminodia bibrachiate, branches elongate-penicillate, 3– 3.5 mm long. Anthers oblong, c. 3 mm long, shallowly bifid, deeply sagittate; filaments 1–1.5 mm long. Style terete, 7–8.5 mm long, distally 3-branched, branches 3 – 3.5 mm long. Capsules dark brown, obovoid, 3 – 5 by 2– 3 mm. Seeds brown to dark brown, translucent, narrowly ellipsoid to oblong, 0.5– 0.8 mm long, 0.2 –0.3 mm diam, with 13–15 longitudinal ridges and with 0 – 4 transverse ridges between the longitudinal ridges.

Distribution — Endemic to Thailand, North-Eastern: Bueng Khong Long, only known from the type locality. It may be assumed that it has a wider distribution in nearby areas along the Mekong basin of Laos and Thailand.

Habitat & Ecology — On open, sandy soil, in wet places in dry dipterocarp forest, at 180 m altitude.

Phenology — Flowering and fruiting: October to December, between the late rainy season and the beginning of the dry season. The flowers open in the morning at 08.30 a.m. and persist until 12.30 p.m.

Vernacular name — Kathin khok.

Specimens examined. Bueng Kan (Bueng Khong Long,Pho Mak Khaeng,

Ban Dong Chomphu, 180 m alt., 17°58'N, 104°05'E): Phonsena 6704 ( KKU) GoogleMaps ,

mm

31 Dec. 2010; Phonsena & Boonsuk 6585 ( BK, BKF, C, K, KKU, L, QBG) , 25 Oct. 2010; Phonsena & Boonsuk 6622 ( BKF, KEP, L) , 28 Nov. 2010.

Conservation status — Xyris emarginata is known from a restricted area which is under pressure from agricultural and urban development. The extent of occurrence is estimated as to be less than 100 km 2. A rating of Critically Endangered (CR, IUCN 2001) is merited.

Note — The fertile bracts of X. emarginata resemble those of X. lobbii Rendle in its emarginate apex, but differ in its lacerate margin (entire in X. lobbii ). The margin of the fertile bracts also resemble those found in X. complanata , but the new species differs from the latter in the leaf margin and the scape being smooth, not rough with tubercles.