Cephalanthus angustifolius Lour. (Loureiro 1790: 67)

Romero, Maria Florencia, Gonzalez, Ana Maria & Salas, Roberto Manuel, 2023, Sylvainia, a new monospecific genus within the subtribe Cephalanthinae (Rubiaceae, Naucleeae), Plant Ecology and Evolution 156 (1), pp. 85-111 : 85

1. Cephalanthus angustifolius Lour. (Loureiro 1790: 67)

Figs 2 , 3

Cephalanthus stellatus Lour. ( Loureiro 1790: 68).

Acrodryon angustifolium (Lour.) Spreng. ( Sprengel 1824: 386).

Nauclea stellata (Lour.) Wall. ( Wallich 1832: 6102).

Axolus angustifolius (Lour.) Raf. ( Rafinesque 1838: 61), non Cephalanthus angustifolius Dippel ( Dippel 1889: 164).

Eresimus stellatus (Lour.) Raf. ( Rafinesque 1838: 61).

Type.

VIETNAM • Loureiro s.n.; holotype: BM [BM000606644]; probable isotype: K [K001123035].

Description.

Shrub or small tree, up to 3 m tall. Leaves (2-)3-verticillate, pseudopetiolate; pseudopetiole subcylindrical, glabrous, 2-5 mm long; blade oblong to narrowly ovate, glabrous, subcoriaceous, discolorous, (3-)5-13 × 1-5 cm, base acute, apex acute or acuminate; veins 3-6 on each side, slightly discolorous, leaf domatia absent; stipules triangular, pubescent on both sides, with dark colleters at the apex and margin, few light colleters on the ventral (inner) side intermingled with numerous trichomes. Inflorescences short pedunculate, peduncle 2-3 cm long, bracteoles spatulate, pubescent, with dark colleters at the apex. Flowers perfect; calyx 4- or 5-lobed, lobes narrowly triangular, pubescent on ventral (inner) side, 1.1-4.0 mm long, margin puberulous, with dark colleters at the interlobular sinuses, infrequent at the margin; corolla hypocrateriform to slightly infundibuliform, 4- or 5-lobed, 5-8 mm long, lobes oblong, 1-2 mm long, with dark colleters at the interlobular sinuses, tube externally glabrous and internally puberulous; stamens 4 or 5, filaments filiform, glabrous, 0.4-0.5 mm long; hypanthium turbinate, glabrous, 0.9-2.0 mm long; style filiform; stigma capitate and exserted at flower maturity. Fruits narrowly obovate, glabrous, 4-5 mm long. Seeds 1.5-2.0 mm long; aril 1.3-1.8 mm long.

Distribution.

The species is found in the easternmost region of the Indochina Peninsula. According to Puff et al. (2021), it is found in Laos and Vietnam, and probably Thailand. However, in the latter country, no collections have been recorded so far. Puff et al. (2021) mentioned "It is not completely confirmed whether the species occurs in Thailand or not. It is likely that a collection from the banks of the Mekong at 16°N (Harmand s.n. (W, P)) has originated on the Laos side of the river and no plants have been collected on the Thai side so far. However, being a rheophyte, it is very likely that it is not restricted to the E. banks of the Mekong". Based on herbarium specimens (HN, F, K, L, NY, P, W), its presence was confirmed for Laos and Vietnam. According to studies of medicinal plants, several authors mentioned that C. angustifolius is present in Cambodia ( Dy Phon 2000; Kham 2004; Ashwell and Walston 2008), however, it was not possible to see the herbarium specimens cited in these studies. The records for this country on the map are based on these citations (Fig. 3 ).

Habitat and ecology.

Cephalanthus angustifolius is a rheophyte, typical of more or less rushing rivers and streams, surrounded by lowland forest, mostly in primary habitats. Some recent collections were made in secondary habitats.

Phenology.

Based on the scarce material analysed, it flowers from November to January and produces fruit from April to June.

Vernacular name.

Khtum kok (Cambodia; Dy Phon 2000); Rì lớn lá, Rì bông gáo, Vậy lá hẹp (Vietnam).

Uses and ethnobotanical aspects.

The leaves are used as an astringent in traditional medicine in Cambodia. The bark infusion is used as an analgesic for general aches and pains. The plant is traditionally prescribed as an analgesic for childbirth pains ( Dy Phon 2000; Kham 2004; Ashwell and Walston 2008).

Additional material examined.

LAOS • Without precise locality, fluminis Mekong; Sep. 1877; Harmand 6270; P [P03820120, P03820119, P03820118], W .

VIETNAM • Tourane; 4-13 Jun. 1927; J. Clemens & M.S. Clemens 3588; P [P03820123]. - Khanh Hoa • Krempf s.n.; P [P03820121] • 20 Jan. 1913; Krempf s.n.; P [P03820124] • Nha Trang , cascades, au milieu du ruisseau ( îlot); 2 Sep. 1953; s.col. s.n.; P [P04560861] • Dien Khanh district , road transact Suoi Cat-Hon Ba , at km 19 to Hon Ba , forest along rocky riverbank of Da Giang River ; 12°06 ’53” N, 109°00 ’12” E; 22 Jun. 2004; Soejarto 13284; F, L, P • Hon Ba Mts , Suoi Village , road transect Suoi Village to peak a km markers 25-24, lowland tropical forest formation along Da Giang river ; 12°7.97'N, 109°1.28E; 110 m; 2 Nov. 2004; Soejarto 13537; F, L, P. - Thua Thiên Hué • Bên Du pro, Thua Thiên, Récolte sur le bord de Sông Bô; 16°31 ’40.8” N, 107°34 ’22.8” E; 13 May 1920; Poilane 1410; K, P [P03820122, P03820077] • [Annam], Thua Thien Hue, Nam Dong, Bach Ma N.P., Huong Loc; 16°8 ’22.99” N, 107°47 ’27.00” E; 137 m; 18 May 2016; Hai 1150; HN, NY .

Notes.

According to Stafleu and Cowan (1981: 174), most of the collections of Loureiro are deposited in BM, while few specimens are also preserved at P and LINN. The remaining collections deposited in LISU were apparently destroyed, without explanation how it happened. After consulting the collections in BM, only one type specimen of Loureiro was found, which coincides with the results of the earlier Cephalanthus revisions ( Haviland 1897; Ridsdale 1976). Loureiro (1790) described C. angustifolius and C. stellatus in the same treatment of Flora Cochinchinensis, separating the first by its opposite leaves (vs verticillate leaves in C. stellatus ). Haviland (1897) noticed that the available type specimen in BM does not match in all aspects with the diagnosis of C. angustifolius , because the specimen has verticillate leaves, while the description mentions opposite. All available specimens of C. angustifolius have invariably verticillate leaves. Similar incongruence, in other taxa of Loureiro, was mentioned for Stapelia cochinchinensis Lour. and S. chinensis Lour. ( Rodda 2016). Some morphological aspects of one type appeared in the description of the other name, and vice versa. As for the type of C. angustifolius and C. stellatus , we follow Haviland in considering them as homotypic synonyms.

Figures

Figure 2. Cephalanthus angustifolius. A. Flowering branch. B. Stipule. C. Partial inflorescence. D. Flower. E. Hypanthium, style, and stigma. F. Corolla at anthesis. G. Ventral view of schizocarp. H. Dorsal view of schizocarp. I. Dorsal view of seed with aril. J. Subventral view of seed with aril. Drawn by Laura Simon.

Figure 3. Distribution map of Cephalanthus angustifolius, C. glabrifolius, and C. tetrandrus.