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FOC | Family List | FOC Vol. 19 | Rubiaceae

39. Ixora Linnaeus, Sp. Pl. 1: 110. 1753.

龙船花属 long chuan hua shu

Authors: Tao Chen & Charlotte M. Taylor

Schetti Adanson; Tsiangia But, H. H. Hsue & P. T. Li.

Shrubs or small trees or occasionally perhaps climbing (Ixora hekouensis), unarmed. Raphides absent. Leaves opposite or rarely ternate, decussate, without domatia; petioles articulate at base; stipules persistent to caducous, interpetiolar or shortly united around stem, triangular, acute to usually aristate. Inflorescences terminal on principal stems [or sometimes terminal on reduced lateral stems and appearing axillary], cymose to corymbiform or paniculiform, few to many flowered, sessile to pedunculate, bracteate or bracts reduced; axes often articulate; bracteoles when present often fused in pairs. Flowers pedicellate or sessile, bisexual, monomorphic, often fragrant. Calyx limb truncate or 4-lobed. Corolla yellow, orange, red, or white, sometimes becoming reddened when dry, salverform with tube slender, inside glabrous or pubescent at throat; lobes 4 [rarely to 9], convolute in bud. Stamens 4, inserted at corolla throat, partially to fully exserted; filaments short or reduced; anthers dorsifixed near base. Ovary 2-celled, ovules 1 in each cell, pendulous from axile placentas attached in upper part of septum; style in upper portion fusiform or clavate; stigmas 2, linear, recurved, exserted. Fruit black or red, drupaceous, leathery or fleshy, subglobose to ellipsoid or ovoid, with calyx limb persistent; pyrenes 2, 1-celled, each with 1 seed, plano-convex or concavo-concave, smooth dorsally (i.e., abaxially), leathery, papery, or crustaceous; seeds medium-sized, ellipsoid to oblanceolate, grooved and concave ventrally (i.e., adaxially); testa membranous; endosperm cartilaginous; radicle terete, hypogeous.

About 300-400 species: widespread in tropical Africa, America, Asia, Madagascar, and Pacific islands; 18 species (nine endemic) in China.

Ixora has been studied in SE Asia only by Bremekamp; he published several articles treating the species of several regions there (cited by De Block, Opera Bot. Belg. 9: 213. 1998) but not specifically treating the Chinese species, although his circumscription of the region "Burma and the Andaman Islands" included some species from Xizang (Bremekamp, J. Bot. (London) 75: 108-111, 169-175, 260-266, 295-298, 318-326. 1937).

Several species of Ixora are widely cultivated in tropical regions as ornamentals, notably I. casei Hance, I. coccinea Linnaeus, I. finlaysoniana, and sometimes I. chinensis. In cultivation several of these have various forms with a wide range of flower color, flower and leaf size, and plant height, and sometimes they do not set fruit. Ixora coccinea and I. casei are not treated in this current flora but are included in the key to species below for identification. Reynolds and Forster (Austrobaileya 7(2): 253-278. 2006) reported that I. coccinea is locally adventive in some parts of Australia, which may be a possibility in China. The most commonly cultivated Ixora species were discussed in detail by Fosberg and Sachet (Baileya 23(2): 74-85. 1989).

Ixora foonchewii was described and illustrated as having consistently 5 corolla lobes and a stout, shortly bilobed stigma, so it does not seem to belong to Ixora; it is provisionally included here in Tarenna.

1 Calyx lobes 3-6 mm   (2)
+ Calyx lobes 0.1-1.5 mm   (4)
2 (1) Leaves relatively narrow, 1-4 cm wide, acute to acuminate at both ends, with secondary veins 12-15 pairs; corolla tube 30-40 mm, lobes 6-7 mm.   18 I. yunnanensis
+ Leaves not notably narrow, 3-9 cm wide, rounded to cuneate at base, obtuse, acute, or acuminate at apex, with secondary veins 9-12 pairs; corolla tube 20-30 mm, lobes 5-6 mm   (3)
3 (2) Corolla lobes obtuse to rounded.   2 I. cephalophora
+ Corolla lobes acute to subacute.   5 I. finlaysoniana
4 (1) Leaves with secondary veins 5 or 6 pairs   (5)
+ Leaves with secondary veins 7-16 pairs   (6)
5 (5) Petioles 0-2 mm; corolla lobes 8-15 mm; flowers variously yellow to red; plants cultivated.   I. coccinea (see comment above)
+ Petioles 2-8 mm; corolla lobes 6-7 mm; flowers white; plants native.   7 I. hainanensis
6 (4) Petioles 10-20 mm, at least some of them more than 10 mm   (7)
+ Petioles 0-10 mm, at least some of them shorter than 10 mm   (12)
7 (6) Leaves shallowly bullate with principal veins impressed on puffy upper surface; corolla white to pink   (8)
+ Leaves plane, with principal veins flat to prominent on flat upper surface; corolla red, purple, yellow-orange, pink, or white   (9)
8 (7) Corolla tube 30-40 mm, lobes 5-7 mm.   12 I. nienkui
+ Corolla tube 15-18 mm, lobes ca. 5 mm.   17 I. tsangii
9 (7) Corolla red, tube ca. 10 mm, lobes ca. 5 mm.   13 I. paraopaca
+ Corolla white, pink, yellow-orange, or red, tube 25-40 mm, lobes 5-15 mm   (10)
10 (9) Stems relatively stout, youngest sections 3-5 mm in diam.; plants cultivated.   I. casei (see comment above)
+ Stems slender, youngest sections 1-3 mm in diam.; plants native   (11)
11 (10) Corollas yellow-orange to red, with lobes 10-12 mm; stipule body (i.e., triangular portion) 2-3 mm.   6 I. fulgens
+ Corollas white to pink, with lobes 5-7 mm; stipule body 3-10 mm.   12 I. nienkui
12 (6) Leaves sessile or subsessile with petioles up to 4 mm, base cordate, cordulate, truncate, cuneate, rounded, or obtuse   (13)
+ Leaves with petioles 2-10 mm, base rounded, cordulate, cuneate, obtuse, truncate, or acute   (17)
13 (12) Corollas red-purple, tube 8-9 mm, lobes 4-5 mm.   11 I. longshanensis
+ Corollas white, red, or purple, tube 13-45 mm, lobes 5-7.2 mm   (14)
14 (13) Corolla lobes broadly obtuse to rounded.   3 I. chinensis
+ Corolla lobes acute to obtuse   (15)
15 (14) Leaves 10-23 × 5.5-9 cm.   1 I. auricularis
+ Leaves 4.5-12 × 2-7 cm   (16)
16 (15) Corolla lobes obtuse.   14 I. philippinensis
+ Corolla lobes acute.   15 I. subsessilis
17 (12) Peduncle ca. 14 cm.   10 I. insignis
+ Peduncle 0.4-5 cm   (18)
18 (17) Inflorescences with tertiary and often also quaternary axes well developed and spreading at 45°-90° or more; corolla tube 7-11 mm.   4 I. effusa
+ Inflorescences with tertiary and quaternary axes developed to reduced and ascending at less than 45°; corolla tube 18-40 mm   (19)
19 (18) Corolla lobes ovate, elliptic, or broadly elliptic, at apex broadly obtuse to rounded.   3 I. chinensis
+ Corolla lobes elliptic-oblong, narrowly elliptic-oblong, ovate-lanceolate, narrowly spatulate, narrowly lanceolate, or oblong-lanceolate, at apex obtuse to acute   (20)
20 (19) Calyx puberulent or glabrescent; corolla tube 18-20 mm, lobes 5-7 mm   (21)
+ Calyx glabrous; corolla tube 20-40 mm, lobes 5-7 mm   (22)
21 (20) Leaves 10-18 cm, at base cuneate to obtuse, at apex acuminate to acute; bracts 3.5-5 mm.   8 I. hekouensis
+ Leaves 4.5-10 cm, at base truncate, rounded, or cordulate, at apex obtuse or rounded and apiculate; bracts 1.5-2 mm.   14 I. philippinensis
22 (20) Leaves 15-17 × 6.5-7.5 cm; stipules villous adaxially.   16 I. tibetana
+ Leaves 4-15 × 1-5 cm; stipules glabrescent adaxially   (23)
23 (22) Low to medium-sized plants, flowering at 0.2-3 m tall; leaves rounded, obtuse, or bluntly acute at apex; corollas with tube 30-40 mm, in bud acute to rather sharply acute.   7 I. hainanensis
+ Medium-sized shrubs, flowering at 1-3 m tall; leaves sharply acute to acuminate at apex; corollas with tube 20-25 mm, in bud sharply acute to acuminate.   9 I. henryi

  • List of lower taxa


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