Euphorbia acolumella Sarojin. & Raja Kullayisw.

Euphorbia acolumella Sarojin. & Raja Kullayisw.

Figs. 1 View Fig & 2 View Fig s p. nov.

This species is closely related to Euphorbia indica

Lam. in its branching pattern, oblong to elliptic leaves, and pubescent stems but differs in its laciniate stipules and bracteole, short peduncles of pistillate flower that are not pendulous, sub-equal limbs, and loculicidal capsules without a columella at the center.

Type: INDIA, Andhra Pradesh, Kadapa District, Mabbuchintalapalli , 14°21’23.8” N, 78°15’22.5” E, 358 m, 05.01.2023, K GoogleMaps . Raja Kullayiswamy DNA-004 (holo MH!; iso BSID!, SKU!) .

Prostrate herbs, up to 25 cm long. Latex milky. Stems branching radially from the stout root stock; stems sympodially branched; branches terete, pubescent; internodes 2.5‒4 cm long; stipules interpetiolar, linear-lanceolate, laciniate, c. 1.5 × c. 1 mm, glandular trichomes present at stipular base, club shaped, 0.5 mm long. Leaves simple, opposite, sub-sessile;petiole c. 1.5 mm long,pubescent;lamina elliptic-oblong, 1‒2 × 0.5‒1 cm, sparsely hairy on adaxial, pubescent on abaxial, base oblique, margin entire, mucronate at apex, midrib prominent, lateral nerves obscure, 3‒4 pairs. Cyathia 3‒20 in axillary and terminal clusters; cyathial peduncles dichotomously branched, c. 3 mm long, pubescent. Involucre of cyathium turbinate, c. 2 mm long, pubescent; involucral bracts laciniate, c. 2 mm long; glands 4, oblong, c. 0.1‒0.2 × 0.4 mm, pink; limb of gland sub-equal, white to pale pink, oblong, c. 0.2 × 0.4‒0.7 mm. Staminate flowers 6–8, inserted within involucre, c. 1 mm long; bracteole laciniate, c. 0.4 mm long; anthers sub-globose, yellow, c. 0.2 mm long, dehiscence transversely. Pistillate flower peduncle c. 1.2 mm long, straight (not laterally pendulous); ovary tricarpellary syncarpous, trilocular; styles three, fused from the base, c. 0.9 mm, long; stigmas simple, bifid at apex. Fruit is a loculicidal capsule, depressed globose, c. 4 mm long, dehisce to the middle (or less) from the top; cocci obscurely keeled, each lobe is free from other lobe; columella absent. Seeds 3 per capsule, ovoid to ovoid-oblong, c. 1.2 × c. 0.7 mm, brown, obscurely transversely furrowed, slightly rugulose.

Flowering & Fruiting: Flowering and fruiting from December to February.

Habitat & Distribution: Euphorbia acolumella is hitherto known from the Palakonda Hills, Kadapa District, Eastern Ghats, Andhra Pradesh, India. Plants were found growing in black gravelly soil, interspersed with calcium rock, in scrub forest near Mabbuchinthalapalli.

Etymology: The specific epithet “ acolumella ” refers to absence of columella in the capsule.

Notes: Euphorbia acolumella belongs to the subgen. Chamaesyce sect. Hypercifoliae , and is allied to E. indica , which is commonly found in cultivated fields. This species is found growing in the plains of scrub forests near the Palakonda Hills in Kadapa District. The plant exhibits unique features in comparison to its morphologically similar taxa such as multiple branches arising from a stout root stock, presence of club shaped glandular trichomes at the base and laterals of the laciniate stipules ( Fig. 2f View Fig ), staminate flowers showing laciniate bracteoles, pediceles of pistillate flower are short and not laterally pendulous, stigmas fused up to middle, bifid at apex, and depressed globose, capsules without columella. The tricarpellary capsule is a generic character of the genus Euphorbia except for E. lathyris L. which is drupaceous. Capsules of Euphorbia are generally 3-lobed, that dehisce to three bivalved cocci usually leaving a central columella. Each coccus splits up longitudinally into three valves along the inner structure ejecting the seed by the elastic twisting of the valves.

Table 1. Comparison between Euphorbia acolumella with allied species.

The presence of a loculicidal capsule and absence of the central columella ( Fig. 2d & k View Fig ) in Euphorbia acolumella is a noteworthy character within the genus Euphorbia , and has not been previously documented. Due to the absence of the columella, the capsule shape became depressed globose, dehisce to the middle (or less) from the top and also is important for seed dispersal. So far, all reported Euphorbia species feature a columella at the centre axis of the capsule.