00. Dentella[1]

J.R.Forst. & G.Forst., Char. Gen. Pl.: 13. 1775.

Prostrate herbs. Leaves opposite, shortly petiolate; stipules membranous, interpetiolar, slightly adnate on both sides to the petioles. Inflorescences uniflorous, flowers singly in leaf axils at alternate nodes or terminal in branch forks. Flowers small, bisexual, 5-merous. Calyx deeply divided into 5 lobes. Corolla infundibular, tube long-hairy inside; lobes induplicate-valvate in bud, much shorter than tube. Stamens inserted slightly above base of tube, subsessile, included. Ovary 2-celled, each locule with numerous ovules on a semi-globose placenta along septum; style with 2-lobed stigma short and included. Fruit crowned by persistent calyx lobes, dry, indehiscent; seeds numerous, angular, reticulate.

A small genus of less than 10 species occurring from tropical and subtropical Asia to the SW. Pacific; 1 species in Thailand.— Classification: subfamily Rubioideae, tribe subfamily Rubioideae, tribe Spermacoceae [previously Hedyotideae].

Dentella repens (L.) J.R.Forst. & G.Forst., Char. Gen. Pl.: pl. 13 (1775); Craib in Fl. Siam. En. 2(1) : 26. 1932.— Oldenlandia repens L., Mant. Pl. 1: 40.1767.—  Hedyotis repens (L.) Lam., Tabl. Encycl. 1: 271. 1792.

Key to the varieties

1.  Ovaries and fruits densely pilose (but mature fruits sometimes becoming glabrescent)   

var. repens

1*.  Ovaries and fruits glabrous

var. serpiphylla

Var. repens

Creeping, much-branched herb, often forming dense mats or cushions up to 0.5 m in diam. Stems obscurely 4-angled to terete, mostly glabrous. Leaves elliptic, oblong-lanceolate or oblong-obovate, 2-10 mm by 1-5 mm, acute at base and apex, glabrous or sparsely hairy on midrib below, lateral veins inconspicuous; petioles glabrous, 2-3 mm long; stipules truncate, entire, to c. 0.5 mm high. Flowers in leaf axils, 1 per node (flowering nodes alternating with non-flowering nodes), rarely terminal; pedicels 0.5-2 mm long. Calyx lobes erect, triangular-lanceolate, c. 0.5-1.5 mm long, acute. Corolla white, 5-15 mm long, glabrous on the outside; tube hairy around the throat; lobes much shorter than tube, often with a purplish spot at the base. Stamens inserted near base of tube, anthers subsessile, < 1 mm long. Ovary (densely) pilose, 2-3 mm high; style plus the 2 coherent stigmas c. 1.5-6 mm long. Fruit crowned by slightly enlarged, erect calyx lobes, glbose, c. 3-4 mm in diam., densely to sparsely covered by stiff, white hairs.

T h a i l a n d.— NORTHERN: Chiang Mai, Kamphaeng Phet; NORTH-EASTERN: Loei; central: Krung Thep Maha Nakhon (Bangkok); SOUTH-EASTERN: Trat; PENINSULAR: Satun.

D i s t r i b u t i o n.— Mauritiuis; India and Sri Lanka to Indochina; Taiwan; SE. throughout Malesia to New Caledonia.

E c o l o g y.— Stream banks, margin of ponds, open meadows, pastures; sometimes a weed in lawns. Altitude: 0–400 m.

V e r n a c u l a r.— ??.

N o t e s.— 1. Plants show considerable, apparently habitat-dependent variability. For this reason neither leaf sizes and shapes nor floral characters, previously used to separate var. repens from var. serpiphylla [see below], provide reliable distinction characters. 2. Probably undercollected and more widely distributed than the available specimens suggest.

Var. serpyllifolia (Wall. ex Craib) Verdc., Kew Bull. 37: 545. 1983.—  Dentella serpyllifolia Wall. ex Craib in Fl. Siam. En. 2(1) : 27. 1932.— Dentella repens var. grandis Pierre ex Pitard in Fl. Gén. I.-C. 3(1): 76. 1922.

Very similar to var. repens but ovary and fruit entirely glabrous.

T h a i l a n d.— NORTHERN: Mae Hong Son, Chiang Mai; central: Krung Thep Maha Nakhon (Bangkok).

D i s t r i b u t i o n.— Mauritius; India to Myanmar; Cambodia; SE. to the Philippines.

E c o l o g y.— As for var. repens.

V e r n a c u l a r.— ??.

N o t e.— Hardly worth recognizing as forms with glabrous ovaries and fruits (var. serpiphylla) sometimes appear to grow intermixed with plants having hairy ovaries and fruits (var repens).

[1] C. Puff