22. Phyllanthus rheophyticus M. G. Gilbert & P. T. Li, Fl. China. 11: 188. 2008.
水油甘 shui you gan
Type: China. Hainan: Changjiang Xian, Ngo Ko Shan, near Tsat Cha village, 9 Jun 1933, S. K. Lau 1901 (holotype, BM; isotype, IBSC); Lingshui Xian, Bai Shui Ling, 18°42'15"N, 109°50'12"E, 600 m, 30 Nov 2000, MO-IBSC expedition to Hainan 272 (paratype, BM).
Species Phyllanthi parvifolii Buchanan-Hamilton ex D. Don adhuc inclusa sed caulibus lignosis rigidis erectis vel ascendentibus, caulibus foliis ad apicibus congestibus semper solitaribus, brachyblastis non vidit, foliis majoribus (6-11 × 2-4 mm, non ca. 2 × 4 mm) manifeste differt.
Erect shrubs, up to 2 m tall, glabrous throughout; stem gray-brown; branchlets usually clustered at tips of stems, to 16 cm, transversely compressed, slightly quadrangular, adaxially flattened to grooved. Stipules ovate-triangular, ca. 1 mm, brownish red; petiole ca. 1 mm, transversely wrinkled abaxially; leaf blade oblong or elliptic, 6-11 × 2-4 mm, thinly leathery, glossy dark green when fresh, drying gray-green, slightly paler abaxially, base slightly obliquely cuneate to rounded, margin revolute, apex acute with brown-reddish mucro; lateral veins 4-7 pairs, abaxially raised in dried material. Plants monoecious. Inflorescence an axillary fascicle, usually bisexual with 2-4 male flowers and 1 female flower. Male flowers: pedicels 1-2 mm; sepals 6, ovate-lanceolate or obovate, 1-2 mm, yellow-white or white-green, margins membranous; disk glands 6, globose; stamens 3; filaments connate for ca. half length; anthers oblong, ca. 0.2 mm, thecae parallel, longitudinally dehiscent, connectives slightly mucronate. Female flowers: pedicels ca. 2 mm; sepals as in male, ca. 1.2 × 0.8-1 mm, thickened and persistent in fruit; disk annular, thin, shallowly 6-lobed, dark and reflexed in fruit; ovary globose, ca. 1 mm in diam., 3-locular; styles 3, connate at base, bifid at apex, lobes slightly revolute. Capsule globose, ca. 3 mm in diam. Seeds brown, segmentiform, ca. 1.5 mm, initially yellowish buff becoming light brown minutely speckled red. Fl. Jun-Sep, fr. Aug-Nov.
● Among rocks in riverbeds, open forests, scrub on moist slopes; 300-600 m. Guangdong, Hainan.
Material of this species, which is locally abundant along some rivers, has been named as the Himalayan species Phyllanthus parvifolius Buchanan-Hamilton ex D. Don. It differs most obviously by the habit, with the leafy branchlets congested toward the apices of the stiffly erect or ascending long shoots, whereas in P. parvifolius leafy stems are produced along the length of the more slender and spreading long shoots and mostly in groups from short shoots. Other differences are the larger leaves (nearly always ca. 4 × 2 mm in P. parvifolius) and the broader stipules. No material available shows both good flowers and mature fruits. The holotype, S. K. Lau 1901 (BM), has the best flowers, whereas the parataype, MO-IBSC expedition to Hainan 272 (BM), has the best fruits. Michael Gilbert has not seen any material from Guangdong. Records of P. parvifolius from Yunnan seem better placed in P. cochinchinensis.