00. Xantonnea[1]

Pierre ex Pitard in Fl. Gén. I.-C. 3(2): 272. 1923.

Small trees or shrubs. Leaves opposite, petiolate, blades coriaceous; stipules interpetiolar, triangular, cuspidate. Inflorescences axil­lary and paired, consisting of much-congested, bracteolate many- to few-flowered cymes. Flowers 4(5)-merous, hermaphrodite. Calyx with a short basal tubular part and oblong-lanceolate lobes. Corolla hypocrateriform, tube hairy at the throat, about as long as the lobes, the latter contorted in bud, spreading to reflexed in open flow­ers. Stamens inserted at the throat; anthers subsessile, exserted. Ovary 2-celled, each locule with 3-4 collateral ovules attached to an apical placenta; style with 2-lobed stigma about as long as corolla tube. Fruit a berry-like drupe with thin endocarp, crowned by persistent calyx lobes; each locule with typically 3 seeds.

A small, ill-known genus of 2 species confined to Indochina and Thailand. Apparently (very) close to Hypobathrum (see p. 000) [and Hyptianthera (see p. 000)] and perhaps not to be upheld; detailed investigations of both genera are needed. Classification: subfamily Ixoroideae, tribe Coffeeae.

Key to the species

1. Leaves to 7 cm long, petioles to 3 mm long; fruit globose, to 6 mm in diam.

1. X. parvifolia

1*. Leaves 8-15 cm long, petioles 5-10 mm long; fruit ovoid, c. 10 mm high

2. X. quocensis

1. Xantonnea parvifolia (Kuntze) Craib in Fl. Siam. En. 2(1): 130. 1932.— Discospermum parvifolium Kuntze, Rev. Gen. Pl. 1: 280. 1891.— Tricalysia parvifolia (Kuntze) Merr., Brittonia 2: 198. 1936.— Xantonnea coffeoides Pierre ex Pitard in Fl. Gén. I.-C. 3(2): 271. 1923.— Xantonnea coffeoides var. salicifolia Pierre ex Pitard in Fl. Gén. I.-C. 3(2): 272. 1923.

Shrub to 4 m tall, often much-branched; youngest parts shortly pubescent, soon becoming glabrous. Leaves thinly coriaceous, elliptic-oblong to linear-oblong, 4-7 by 1-3.5 cm, gradually narrowed to the base, apex acute to acuminate, glabrous; 7-9 pairs of lateral veins; petioles short, up to 5 mm long; stipules triangular, with a long apical awn, 4-9 mm long. Inflorescences axil­lary and paired, consisting of  much-congested, dense, subsessile, bracteose, several-flowered cymes. Flowers 4-merous, fragrant. Calyx tube < 0.5 mm high, lobes to 1 mm long, elliptic. Corolla white to creamy-white, tube c. 2.5 mm long, hairy at the throat, lobes to 3.5 mm long, obtuse. Stamens subsessile, anthers c. 1.5 mm long, at least partly exserted. Ovary to c. 1 mm high; style plus 2-lobed stigma to c. 3 mm long. Drupe globose, c. 4-6 mm in diam., crowned by the persistent calyx lobes. Seeds 3-4 per locule, dorsally convex and ventrally concave, c. 3.5-4.5 by 3-4 mm.   

T h a i l a n d.— EASTERN: Buri Ram, Roi Et, Ubon Ratchathani; central: Saraburi, Krung Thep Maha Nakhon (Bangkok; cultivated); SOUTH-EASTERN: Prachin Buri.

D i s t r i b u t i o n.— Laos, Cambodia, Vietnam (type).

E c o l o g y.— Evergreen forest along streams; riverbanks, edge of rice fields; sometimes associated with limestone. Altitude: 20–200 m.

V e r n a c u l a r.— ??.

N o t e s.— 1. Poorly known and not recollected in recent years.
2. Possibly a facultative rheophyte (“var. salicifolia”); needs confirmation in the field.

2. Xantonnea quocensis Pierre ex Pitard in Fl. Gén. I.-C. 3(2): 272. 1923; Craib in Fl. Siam. En. 2(1): 130. 1932.

Glabrous tree to 25 m tall.  Leaves coriaceous, elliptic, oblong or oblanceolate, 8-15 by 3-5 cm, narrowed to the base, apex (shortly) acuminate; 6-7 pairs of lateral veins: petioles 5-10 mm long; stipules triangular, cuspidate, to c. 4 mm long. Inflorescences axil­lary and paired, consisting of dense clusters of subsessile flowers arranged in much-congested, bracteose, several-flowered cymes. Flowers 4-merous, only known from bud stage. Buds c. 3 mm long. Stamens subsessile. Ovary with 3 ovules per locule. Drupe ovoid, c. 10 mm high and 9 mm wide, crowned by the persistent calyx. Seeds 3 per locule, dorsally convex and ventrally flat or concave, c. 6-6.5 by 5 mm.

T h a i l a n d.— NORTHERN: Phitsanulok; SOUTH-EASTERN: Prachin Buri, Rayong.

D i s t r i b u t i o n.— Cambodia (type), Vietnam.

E c o l o g y.— Evergreen and semi evergreen forest. Altitude: ?–200–? m.

V e r n a c u l a r.— ??.

N o t e.— Poorly and incompletely known and not recollected in recent years.

 



[1] C. Puff