Parainvolucrella scabra (Wall. ex Kurz) M.D. Yuan & R.J. Wang, 2021

Xu, Yi-Da, Yuan, Ming-Deng & Wang, Rui-Jiang, 2021, Morphology and molecules support the new monotypic genus Parainvolucrella (Rubiaceae) from Asia, PhytoKeys 180, pp. 53-64 : 53

Parainvolucrella scabra (Wall. ex Kurz) M.D. Yuan & R.J. Wang comb. nov.

Figs 2 , 3

Hedyotis scabra Basionym: Hedyotis scabra Wall. ex Kurz, J. Asiat. Soc. Bengal, Pt. 2, Nat. Hist. 46(2): 133, 136 (1877). Type: MYANMAR. from Martaban down to Upper Tenasserim, Wall. Cat. 880 (holotype: CAL; isotypes: G [G00436284!; G00436285!]; K [K001110148!; K001110149! K000031881!]).

Scleromitrion scabrum Synonym: Scleromitrion scabrum (Wall. ex Kurz) Neupane & N.Wikstr., Taxon 64(2): 317 (2015)

Description.

Annual or perennial herbs. Stems decumbent, ca. 1 m long, roughly angular, usually rooted at nodes; branches ascending to 30 cm high. Leaves opposite, subsessile to petiolate, petiole to 3 mm long; blades 2.0-7.0 × 1.0-3.0 cm, narrowly ovate to ovate, apex acute, base cuneate; leaf scabrid adaxially and along the veins abaxially; mid-rib depressed adaxially and prominent abaxially; secondary veins 5-6 on each side. Stipules ca. 3.0 × 2.0 mm, triangular, fimbriate with tipped colleters, excurved, pubescent abaxially. Inflorescence terminal, (2-)3-8(-12)-flowered, congested-cymose, usually subtended by 4 involucral leaves; peduncle subsessile; bracts 2-3 mm long, narrowly ovate, scabrid; bracteoles ca. 1 mm long, truncate to broadly ovate-triangular, fimbriate with tipped colleters, glabrous. Flowers heterostylous, pedicels to 0.8 mm long. Hypanthium ca. 0.8 mm long, obconic, 4 longitudinal projections against the lobes; lobes 4, ca. 1.5 × 0.4 mm long, narrowly triangular to narrowly oblong, scabrid. Corolla white, tube 1.5-2.0 mm long, glabrous abaxially and pubescent adaxially; lobes 4, 2.3-2.8 × 0.7-0.8 mm, oblong. Stamens 4, anthers 0.6-0.7 mm long. Stigma bilobed, 0.5-0.6 mm long, papillate. Longistylous flowers: stamens included, filaments adnate to the base of corolla tube, filaments ca. 2 mm long; styles ca. 4.3 mm long, exserted, included part pubescent, stigma ellipsoid. Brevistylous flowers: stamens included; filaments adnate to the base of corolla tube, filaments ca. 5.6 mm long; styles ca. 2 mm long, exserted, pubescent, stigma clavate. Fruits ca. 2.1 × 2.3 mm, subglobose, with 4 longitudinal projections when young, scabrid, indehiscent. Seeds trigonous, 0.4-0.5 mm, numerous, black; testa reticulate.

Phenology.

Flowering from July to September; fruiting from October to December.

Etymology.

The generic name Parainvolucrella alludes to similarity to Involucrella coronaria in possessing terminal inflorescence subtended by four involucral leaves.

Distribution and habitat.

Bangladesh, India, Myanmar, Thailand and Vietnam ( Fukuoka 1970; Dutta and Deb 2004), and China (new record). Only one subpopulation including about 200 individuals was found in dense bamboo forest and at the edge of the forest nearby the Nonggang National Nature Reserve. The habitat there belongs to a tropical monsoon climate, main associated species are Dendrocalamus latiflorus Munro ( Poaceae ) and Centotheca lappacea (L.) Desv. ( Poaceae ).

Palynology.

Monads, isopolar and prolate-spheroidal, with 3-colporate apertures; the tectum is double microreticulate, with a psilate suprareticulum and a microechinate infrareticulum. The pollen size is 22.2 (20.9-23.7) × 20.2 (18.3-21.8) μm with P/E value 1.10 in brevistylous flowers (Fig. 4A-C ); and 20.2 (18.5-21.2) × 19.0 (16.6-20.6) μm with P/E value 1.06 in longistylous flowers (Fig. 4D-F ).

Additional specimens examined.

China. Guangxi Zhuang Autonomous Region: Chongzuo City , Longzhou County, Zhubu Town , Nonggang Village , 1 Nov 1978, Nonggang Investigation Team 11263 (IBK!); same locality, 22°29'16"N, 106°56'13"E, elev. 287 m, 29 Oct 2020, Ming-Deng Yuan & Yi-Da Xu YS 398, YS399 (IBSC!); same locality, 22°29'22"N, 106°56'11"E, elev. 290 m, 2 Feb 2021, Ming-Deng Yuan YS 407 (IBSC!); Zhubu Town , Lenglei Village , 9 Oct 1979, Nonggang Investigation Team 20457 (GXMI!) . India. India orientalis: in Bengalia circa Calcuttam, J.W.Helfer 40 (P03904580) . Thailand. Kampeng: A.F.G. Kerr 6161 (SING!); Tak: Ban Musoe , 22 Jul 1973, Gen Murata et al. 16719 (P03904581) .

Figures

Figure 2. Parainvolucrella scabra (Wall. ex Kurz) M. D. Yuan & R. J. Wang A habit B leaf adaxial (left) and abaxial (right) surface C stem and stipule D infructescence with four involucral leaves E infructescence with bracts F calyx with bracteole at base G-I longistylous flower J-L brevistylous flower M, N fruits O seeds.

Figure 3. Seed morphology of Parainvolucrella scabra A ventral side B dorsal side C testa ornamentation.

Figure 4. Pollen morphology of Parainvolucrella scabra (A-C from Mingdeng Yuan & Yida Xu YS 398, brevistylous flower D-F from Mingdeng Yuan & Yida Xu YS 399, longistylous flower) A, D equatorial view B, E polar view C, F double microreticulate ornamentation of mesocolpium.