Itea riparia Collett & Hemsl., J. Linn. Soc., Bot. 28: 57. 1890.

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

1. Itea riparia Collett & Hemsl., J. Linn. Soc., Bot. 28: 57. 1890.

Figs 1 , 2 , 3 , 4

Itea thorelii = Itea thorelii Gagnep., Notul. Syst. (Paris) 3: 222.1916. Type. Laos. Luang-prabang, 1866-1868, Thorel 3474 (lectotype: P00709632, photo!, designated by Lecompte 1965: 40; isolectotypes: P00709633 photo!, P00709634 photo!).

Itea tenuinervia = Itea tenuinervia S. Y. Liu, Guihaia 21(1): 35. 2001. Type. China. Guangxi Province, Daxin County, Shuolong Town, by stream, 14 Jan 2000, Shou-Yang Liu 2893 (holotype: GXCM; isotype: IBK00190789!), syn. nov.

Type.

Myanmar. Southern Shan States , Shan hills, on river-banks, 2000-4000 feet (ca. 700-1400 m) elev., H. Collett s.n. (holotype, K) .

Description.

Shrub, evergreen, usually 0.5-2 m tall, sometimes up to 7 m. Stipules subulate, 0.2-0.7 mm long, caducous. Leaves alternate, both surfaces glabrous, chartaceous, lanceolate or oblanceolate, 3.5-13 cm long, 1-5 cm wide, length/width ratio is 2.6-5.2 (mean = 3.6), acute or slightly acuminate at apex, cuneate at base, distantly shallowly subglandular crenate-serrate along upper margin; mid-vein raised on both surfaces, lateral veins in 4-7 pairs, arcuate ascending, lateral and reticulate veins visible and impressed above surface; petiole 0.4-1.2 cm long, raised above. Pseudoracemes, terminal or sometimes also axillary, usually solitary, sometimes with short branches at base, 4-18 cm long, rachis puberulous, usually 2- or 3-flowered per node; bracts at base of pedicel, subulate, 2-3 mm long, 0.3-0.5 mm wide, deciduous. Flowers white; pedicel erect, puberulous, 3-11 mm long; calyx shallowly cupular; calyx lobes 5, triangular, green, 1.5-2 mm long, 1.2-1.5 mm wide at base, puberulous; petals 5, white, triangular-lanceolate, acute at apex, widest at base, ca. 5 mm long, 1.5-1.9 mm wide at base, glabrous, erect-spreading at anthesis, becoming green and thickened at fruiting; stamens 5, alternating with the petals, shorter than petals, 3.3-3.6 mm long; filaments glabrous, ca. 0.8 mm wide; anthers oblong, ca. 0.6 mm long, 0.4 mm wide; floral disc annular, fleshy, slightly yellow; ovary semi-inferior, consisting of two carpels diverging in the middle and united at the top; stigma capitate. Capsule glabrous, 5-8 mm long, consisting of two obviously divergent carpels, with persistent sepals and petals, turning brown and dehiscing along the ventral suture at mature. Seed numerous, white at immature and brown at mature, 1-1.7 mm across; testa slightly granular.

Distribution.

The species is distributed in China, Laos, Myanmar, Thailand and Vietnam (Fig. 6 ). It usually occurs near streams under forests, with elevation range from 200 to 1400 m.

Specimens examined.

China. Guangxi: Daxin , 15 May 2008 , Guangxi Exped. Inst. Bot. 498 (IBK00278403), 17 Sept 2004 , Shou-Yang Liu F000749 (GXMI014126), 400 m elev., 9 Jun 2023, 22.854261°N, 106.725634°E, Zhu-Qiu Song et al. JZ20230549 (IBSC); Jingxi , 457 m elev., 30 June 2013 , En-De Liu 3996 (KUN1241727), 500 m elev., 10 May 2023, 22.991658°N, 106.674116°E, Bu-Yun Zhang et al. JZ20230371 (IBSC), 500 m elev., 9 Jun 2023, 23.009193°N, 106.659319°E, Zhu-Qiu Song et al. JZ20230553 (IBSC); Napo , 450 m elev., 18 May 1943 , Pu-Chin Tsoong & Ko-Zen Kuang 356 (PE00865551, PE00865552), 15 Apr 1977, Yuan Lin et al. 3-5104 (GXMI014127, GXMI014128). Yunnan: Cangyuan, 700 m elev., 29 May 1974 , Yan-Hui Li 11737 (HITBC015745, HITBC015750, IBSC0273493, KUN0477791, KUN0540565, KUN0540567), 790 m elev., 15 May 1979, Yan-Hui Li 20907 (HITBC015744, HITBC015751, KUN0540559, KUN0540568); Jinghong , 540 m elev., 7 May 1955 , Kuo-Mei Feng 20754 (IBSC0273491, KUN0477788, KUN0477789, PE00865549, SZ00179768), 30 Aug 2019, Yun-Hong Tan ML 56 (XSBN002276); Malipo , 1100 m elev., 21 Jun 1940 , Chi-Wu Wang 86321 (KUN0477792, PE00865553), 1000 m elev., 3 Feb 1940, Chi-Wu Wang 86599 (KUN0477790); Mengla , 17 Jan 1976 , Lai-Yun Xiao 11269 (HITBC099861, IBSC0273492), 680 m elev., 18 Dec 1986, Shao-Rong Guo 592 (IMDY0008066), 850 m elev., 11 Feb 1960, Yan-Hui Li 2813 (HITBC015743, IBK00170997, IBSC0273495, KUN0477787), 560 m elev., 14 Apr 1961, Yan-Hui Li 3049 (HITBC015746), 11 May 1961, Yan-Hui Li 3222 (HITBC015747, IBSC0273494, KUN0477785), Jun 1967, Yunnan First Section 138 (PE00865550), 600 m elev., 2 Sept 2023, 21.989364°N, 101.368001°E , Zhu-Qiu Song et al. JZ20231022 (IBSC); Zhenkang , 12 Apr 1976 , Yan-Hui Li 20116 (HITBC015748, HITBC015749, KUN0477786). Laos. Champasak: Paksong , 29 Apr 2013 , H ang Sun et al. sunhang16056 (KUN1256568, KUN1256569); Luang Namtha: Nateuy , 1130 m elev., 21 Apr 2006 , En-De Liu 1686 (KUN1204594); Luang Prabang: 1866-1868, Thorel 3474 (P00709632, P00709633, P00709634); Phongsal : 30 Apr 1993 , Guo-Da Tao et al. 930162 (HITBC059236, HITBC059244); Vientiane: Mt. Phu Kao Kwai , 700-800 m elev., 31 Dec 1993 , N. Fukuoka & H. Koyama L-65039 (L4134635); Without precise locality, H. Bon s.n. (P03179260) . Myanmar. Maymyo: 760 m elev., 21 Apr 1916 , A. Rodger 510 (NAS00337458), 1066 m elev., 8 May 1912, J. H. Lace 5802 (E00397666), 1066 m elev., 4 May 1912 , J. H. Lace s.n. (E00397667); Taunggyi : 1219 m elev., Apr 1939 , F. G. Dickason 8273 (E01033109). Thailand. Chaiyaphum: Phu Khieo, 600-700 m elev., 1972, K. Larsen et al. 31288 (L1861211), Ban Nam Phrom , 600 m elev., 24 May 1974 , R. Geesink et al. 6886 (L1861215, P00392452); Chiang Mai: Thawatchai, Kasem , 700 m elev., 7 May 1991 , Guo-Da Tao et al. 653 (KUN0540552), Me Ka Pak Bank , 1300 m elev., 21 Apr 1928 , H. B. Garret 505 (L1861224, L1861225, P03179261), Mae Rim District , 600 m elev., 12 Jun 2009 , J. F. Maxwell 09-162 (L2058714, P00911865), Doi Sutep, Mae Sa Falls , 10 Apr 1989 , J. F. Maxwell 89-446 (L1861217), Doi Intson National Park , 650 m elev., 4 May 1997 , J. F. Maxwell 97-443 (L4160466), Doi Inthanon , 1400 m elev., 3 Jan 1975 , R. Geesink et al. 8048 (L1861214, P03371228), Doi Inthanon , 920-960 m elev., 21 Jul 1988 , S. Tsugaru T-61686 (L4161221), 18 Aug 1970, Voravut 8 (L1861218); Kanchanaburi: Sangklaburi, Toong Yai Narssuan Wildlife Reserve , 200 m elev., 12 Jan 1994 , J. F. Maxwell 94-10 (L4134592), near Khwae Noi River, Pompee Village , 250 m elev., 25 Mar 1968 , C. F. van Beusekom & C. Phengkhlai 108 (L1861220), 800 m elev., 30 Apr 2004 , M. van de Bult 796 (L4160559); Nakhon Ratchasima: Khao Yai , 800 m elev., 25 Mar 1968 , B. Hansen et al. 11340 (L1861219, L1861221); Phrae: Mae Bhaem stream, 440 m elev., 5 Jan 1972 , C. F. van Beusekom et al. 4661 (L1861223); Tak: Pha Charoen Waterfall National Park , 20 June 2005 , Pooma et al. 5329 (L4160075), Lansang National Park , 600 m elev., 21 Jul 1973 , G. Murata et al. 16617 (L1861212, P03179258), Lan Sang National Park , 250-400 m elev., 30 Aug 1967 , M. Tagawa et al. 8558 (L1861213), Larn Sarng Nat. Park , 350 m elev., 29 May 1973 , R. Geesink et al. 5532 (L1861222, P03179259); Without precise locality, Apr 1921 , A. F. G. Kerr 5273 (TCD0016587), Mar 1924 , A. F. G. Kerr 8763 (TCD0016588). Vietnam. Dak Lak: Lak, Chu Yang Sin National Park , 900 m elev., 23 Mar 2013 , M.S. Nuraliev 724 (MW0738997); Hoa Binh: Yen Thuy, Cuc Phuong National Park , 12 Sept 2002 , M. V. Xinh MVX 241 (L1861216), Barrage de Cho-bo ( Riviere Noire ), sur les roches calcaires atteintes par les hautes eaux, 18 Oct 1888 , Balansa 3152 (P00709635).

Taxonomic notes.

In the protologue, Liu (2001) considered that I. tenuinervia is distinguished from I. riparia in the height (1-2 m vs. 6 m), leaf shape (long elliptical, rarely oblanceolate vs. oblong, elliptical to lanceolate), pedicel length (10 mm vs. 3-5 mm) and petal length (6 mm vs. 4 mm) and it is distinguished from I. thorelii in the leaf shape (long elliptical, rarely oblanceolate vs. oblanceolate), inflorescence type (racemes vs. racemose panicles), bract shape (triangular-lanceolate vs. linear-lanceolate), petal shape (narrowly lanceolate var. oblong-triangular) and pedicel length (10 mm vs. 4-6 mm). Subsequently, the species was accepted by Chen and Liu (2015). However, our examination of literature and specimens showed that there are no obvious differences between I. tenuinervia and I. riparia (including I. thorelii ) in the characters above (see Table 1 , Fig. 1 ). In the protologue, Liu (2001) did not describe the fruits of I. tenuinervia , but he collected a fruiting gathering at the type locality in 2004, i.e. Shou-Yang Liu F000749, which shows two obviously divergent carpels per fruit (Fig. 1B ). The fruits with two obviously divergent carpels are very special in the genus Itea , because most species bear two partly or completely fused carpels before dehiscence ( Jordaan 2012) and only Itea riparia (including I. thorelii ) was found to have two obviously divergent carpels (see Lecompte (1965: Pl. IV 8-10); Wu (1977: Pl. 26)). Thus, in the fruit character, I. tenuinervia is very similar to I. riparia as well. Furthermore, our observations of living plants in the wild, including in the type locality of I. tenuinervia , also showed that I. tenuinervia is consistent with I. riparia in the morphological characters and habit (Figs 2 - 4 ).

Figures

Figure 1. Itea riparia A isotype of Itea tenuinervia (Shou-Yang Liu 2893, IBK 00190789, https: // www. cvh. ac. cn / spms / detail. php? id = c 1 cf 1 dd 4) B topotype of Itea tenuinervia (Shou-Yang Liu F 000749, GXMI 014126), showing two divergent carpels per fruit C specimen of Itea riparia from Myanmar (J. H. Lace s. n., E 00397667, https: // data. rbge. org. uk / herb / E 00397667), showing two divergent carpels per fruit D lectotype of Itea thorelii (Thorel 3474, P 00709632, https: // science. mnhn. fr / institution / mnhn / collection / p / item / p 00709632), showing two divergent carpels per fruit.

Figure 2. Itea riparia from Jingxi County, Guangxi, China A habitat B-C terminal inflorescences D leaves in adaxial and abaxial views E inflorescences F flowers with the different parts separated G infructescence, showing two divergent carpels per fruit and persistent sepals and petals H fruits and seeds. Voucher specimens: Bu-Yun Zhang et al. JZ 20230371 (fl., IBSC), Zhu-Qiu Song et al. JZ 20230553 (fr., IBSC). Scale bars: 2 cm (B, D); 5 mm (F); 1 cm (H).

Figure 3. Itea riparia from Daxin County, Guangxi, China A habitat B leaves in adaxial and abaxial views C fruiting branchlets D infructescence E fruits, showing two divergent carpels per fruit and becoming green and thickened petals and persistent sepals and petals. Voucher specimens: Zhu-Qiu Song et al. JZ 20230549 (IBSC). Scale bar: 2 cm (B).

Figure 4. Itea riparia from Mengla County, Yunnan, China A habitat B habit C leaves D fruiting branchlet E part of infructescence F fruits and seeds, showing two divergent carpels per fruit. Voucher specimens: Zhu-Qiu Song et al. JZ 20231022 (IBSC). Scale bars: 2 cm (C); 5 mm (F).

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