Itea amoena Chun, Sunyatsenia 1(4): 238. 1934.

Song, Zhu-Qiu & Zhang, Bu-Yun, 2024, Taxonomic notes on the genus Itea (Iteaceae), PhytoKeys 239, pp. 59-72 : 59

2. Itea amoena Chun, Sunyatsenia 1(4): 238. 1934.

Fig. 5

Type.

China. Guangxi Province, Shangsi County, Shup-man-tai Shan [Shi Wan Da Shan], in shaded ravine, about 1200 ft. (ca. 400 m), 29 Jul 1933, Ching-Lieh Tso 23439 (lectotype, designated here: IBSC0004326, isolectotypes: IBSC0004324, IBSC0004325, PE00864804) .

Description.

Shrub, evergreen, usually 0.2-0.5 m, sometimes up to 2 m tall, glabrous, except puberulent on inflorescences. Stipules subulate, ca. 2 mm long, caducous. Leaves alternate, both surfaces glabrous, thinly leathery, narrowly lanceolate, 6.5-13.9 cm long, 1.2-2.2 cm wide, length/width ratio is 4.1-9.5 (mean = 6.5), acuminate or gradually acute at apex, cuneate or subobtuse at base, distantly shallowly subglandular crenate-serrate along upper margin; mid-vein raised on both surfaces, lateral veins in 6-8 pairs, arcuate ascending, lateral and reticulate veins obviously visible and prominently elevated above surface; petiole 1-1.5 cm long, narrowly grooved above. Pseudoracemes, terminal or sometimes also axillary, solitary, 6-24 cm long, rachis puberulous, usually 2- or 3-flowered per node; bracts at base of pedicel, subulate, ca. 1-2 mm long, deciduous. Flowers white; pedicel erect, puberulous, 5-9 mm long; calyx shallowly cupular; calyx lobes 5, narrowly lanceolate, green, 2-2.5 mm long, 0.8-1 mm wide at base, puberulous; petals 5, white, reflexed at anthesis, deciduous at fruiting, triangular-lanceolate, acute at apex, widest at base, ca. 5 mm long, ca. 1.5 mm wide at base, glabrous; stamens 5, alternating with the petals, shorter than petals, ca. 4 mm long; filaments glabrous, ca. 0.3-0.4 mm wide; anthers oblong, ca. 0.5 mm long, 0.3 mm wide; floral disc annular, fleshy, slightly yellow; ovary semi-inferior, narrowly grooved, consisting of two united carpels; stigma capitate. Capsule suboblong-conical, 5-6 mm, glabrous, turning brown and dehiscing septicidally at mature, with persistent sepals. Seed numerous.

Distribution.

The species is only found in Guangxi, southern China (Fig. 6 ). It usually occurs near streams under evergreen forests, with elevation range from 90 to 800 m.

Specimens examined.

China. Guangxi: Dongxing City, Malu, 107°58'56"E, 21°41'8"N, 90 m elev., 12 Oct 2018, Dongxing Exped. 450681181012069LY (GXMG0206492, IBK00418425), 21 Jun 1919, Kuan-Kwang Tsoong 1868 (PE00864807), 26 Sept 1973, Chou-Fen Liang 33611 (IBK00170636); Fangchenggang City, Pingwang, 15 Jul 2007, Feng-Juan Mou 127 (IBSC0712193), Banba, 15 Oct 1973, Chou-Fen Liang 33875 (IBK00170634), Nangui, 11 Nov 1958, Chao-Chien Chang 13197 (IBK00170635, IBSC0272608), Naliang, 24-31 Jul 1936, Wai-Tak Tsang 26510 (IBSC0272609, P03179693), Naliang, 105 m elev., 13 Apr 1956, Hepu Pl. Exped. 2365 (IBSC0272605, PE00864802), Naliang, 107°47.563'E, 21°47.218'N, 140 m elev., 13 Jan 2016, Pu Zou & Kai Xu zp57 (IBSC0824452); Nalungou, 350 m elev., 21 Jul 1982, Peng-Cheng Huang 216 (NF2011745, NF2011746); Shangsi County, Shi Wan Da Shan, 325 m elev., 9 Nov 1958, Chao-Chien Chang 12233 (IBSC0272601), Wangle , 107°49'36"E, 21°53'24"N, 221 m elev., 1 Apr 2009, Wei-Bin Xu et al. liuyan0208 (KUN0906334, KUN0902457), Shi Wan Da Shan , 8 Jul 1937, H. Y. Liang 69500 (IBK00170632, IBK00170633, IBSC0272602, PE00864803), Shi Wan Da Shan , 11-30 Jul 1934, Wai-Tak Tsang 23804 (IBSC0272603), 15-24 Aug 1936, Wai-Tak Tsang 26675 (IBSC0272604, P03179692), Seh-feng Dar Shan [Shi Wan Da Shan], 2500 feet (ca. 800 m) elev., 21 Oct 1928, Ren-Chang Ching 8059 (IBSC0272600, N117066318, PE00864805, PE00864806, US03684023) , 250 m elev., 14 Aug 1986, Beijing Youth Exped. 718 (PE01869678), 90 m elev., 23 Dec 1943, S. H. Chun 3304 (IBSC0272607), 170-300 m elev., 24 May 1944, Shao-Hing Chun 5209 (IBSC0272606), 140 m elev., 8 Jun 2023, 21.097495°N, 108.257582°E, Zhu-Qiu Song et al. JZ20230531 (IBSC), 320 m elev., 8 Jun 2023, 21.882874°N, 107.8346332°E, Zhu-Qiu Song et al. JZ20230537 (IBSC).

Taxonomic notes.

Itea amoena can be readily distinguished from I. riparia in its long narrower leaves (length: width = 4.1-9.5 and ratio mean = 6.5 vs. 2.6-5.2 and 3.6), raised lateral and reticulate veins in the adaxial leaf surface (vs. impressed veins), floral petals reflexed at anthesis (vs. floral petals erect at anthesis), floral petals deciduous at fruiting (vs. becoming green and thickened at fruiting), lanceolate calyx lobes (vs. triangular calyx lobes) and fruits with two fused carpels (vs. two obviously divergent carpels). In distribution, I. amoena is restricted to southern Guangxi and it does not overlap with I. riparia (Fig. 6 ).

Figures

Figure 5. Itea amoena from Shangsi County, Guangxi, China A habitat B leaves in adaxial and abaxial views C flowering branchlet D branchlet E part of inflorescences, showing usually 2 or 3 flowers per node F part of inflorescences, showing floral petals reflexed at anthesis G flowers with the different parts separated H flowers at the end of flowering, showing two fused carpels per fruit and deciduous petals I mature fruits. Voucher specimens: Zhu-Qiu Song et al. JZ 20230531, JZ 20230537 (IBSC). Scale bars: 2 cm (B); 4 cm (C); 5 mm (G).

Figure 6. Distribution map of Itea riparia (green circles) and Itea amoena (red squares).