Shrubs, often climbing, up to 3 m long; branches glabrous to scabrous, divaricate; hairs short, simple. Leaves oblong-ovate, 2-4.5(-9) cm long, 0.7-2.5 (-4) cm broad, entire; apex obtuse, retuse, often slightly mucronate; petiole 2-6 (-8) mm long. Flowers usually in dense, corymbose racemes, greenish-white, pedicellate. Sepals 4, ovate-elliptic, acute or slightly acuminate, margin white-pubescent; calyx-tube 3-8 mm long; calyx lobes 6-14 mm long and 3-7 mm broad. Petals 4, elliptic, 3-8 mm long and 2-5 mm broad, acute, margin a somewhat undulate. Torus about as long or slightly exceeding the calyx tube. Stamens many, inserted on the torus; filaments radiating. Gynophore 1.5-2.5 cm long, with a cylindrical, glabrous, 2-4 mm long ovary. Fruit cylindrical, 3-8 cm long, 1-1.5 cm broad, torulose or irregularly many knotted, pale brown, often somewhat twisted; seeds 5-8 mm in diam., globose, tuberculate.

Type: W. India, collector not known (G).

Distribution: W. Pakistan, India and Ceylon.

A very variable species with regards to hairiness and size of leaves. It is very closely related to M. oblongifolia (Forssk.) A. Rich., from Arabia and Trop. Africa, differing in leaf texture and shape only. M. oblongifolia has thick textured leaves, almost linear and with a single mid rib only, while this species has thinner leaves, more or less ovate-elliptic with a mid rib and conspicuous secondary veins. The resemblance in the two species is so close that Pax & Hoffm. (l.c.) gave the range of distribution of M. arenaria as India and Arabia, while Elffers et al (l.c.) considered the Arabian plants to belong to M. oblongifolia.

Among the gatherings cited above, Jafri 2702 from Laki hills in Sind, has very robust habit with larger leaves, and appearance somewhat different from the rest of the gatherings from W. Pakistan. This needs further studies, especially cytological, from fresh gatherings from that area.