Convolvulus thomsonii Baker, Bull Misc. Inform. Kew 1894: 67. 1894. (Baker 1894: 67).

Wood, John R. I., Williams, Bethany R. M., Mitchell, Thomas C., Carine, Mark A., Harris, David J. & Scotland, Robert W., 2015, A foundation monograph of Convolvulus L. (Convolvulaceae), PhytoKeys 51, pp. 1-282 : 81-82

38. Convolvulus thomsonii Baker, Bull Misc. Inform. Kew 1894: 67. 1894. (Baker 1894: 67).

Convolvulus sagittatus subvar. villosus Hallier f., Bull. Herb. Boissier 6: 533. 1898, as " Convolvulus sagittatus var. parviflorus Hallier f. subvar. villosus Hallier f." ( Hallier 1898a: 533). Type. Based on Convolvulus thomsonii Baker

Convolvulus sagittatus var. villosus (Hallier f.) Rendle, Fl. Trop. Africa (Oliver et al.) 4(2): 96. 1905. ( Baker and Rendle 1905: 96). Type. Based on Convolvulus subvar. villosus Hallier f.

Convolvulus bussei Pilg., Bot. Jahrb. Syst. 41: 295. 1908. ( Pilger 1908: 295). Type. TANZANIA, Songea District, Busse 938 (holotype B†; isotype EA).

Convolvulus hallierianus Schulze-Menz, Notizbl. Bot. Gart. Berlin-Dahlem 14: 377. 1939. ( Schulze-Menz 1939: 377). Type. TANZANIA, Matengo hills, Zerny 17 (holotype W!).

Convolvulus zernyi Schulze-Menz, Notizbl. Bot. Gart. Berlin-Dahlem 14: 377. 1939. ( Schulze-Menz 1939: 377). Type. TANZANIA, Matengo hills, Zerny 370 (holotype W!).

Type.

TANZANIA, N. of Lake Nyasa, Thomson s.n. (holotype K!).

Description.

Prostrate perennial herb, densely tomentose on all vegetative parts, often brownish when dry. Leaves petiolate, 1.2-5 × 0.5-2.5 cm, variable in shape, ovate, lanceolate-deltoid or, most commonly oblong, margin undulate to crenate, base hastate to sagittate; petioles 3-6 (-20) mm. Flowers solitary, axillary, pedunculate; peduncles solitary or, occasionally, paired, 1.5-4 cm, often arching; bracteoles 5-7 mm, linear; pedicels 3-8 (-15) mm; outer sepals 9-11 × 5 mm, ovate, acute to shortly acuminate, densely hairy; corolla (1.3-)1.5-1.8 cm long, white, unlobed, midpetaline bands pubescent, terminating in a tooth; ovary glabrous. Capsule glabrous; seeds glabrous, nearly smooth but somewhat rugose on the angles. [ Verdcourt 1963: 42 (as Convolvulus zernyi )]

Distribution.

Malawi (Synge WC 251, Pawek 13111, Richards 20646); Tanzania (Lovett et al. 2089, Mgaza 121). 1800-2100 m.

Notes.

We have widened the concept of this species from that of Verdcourt (1963) to include plants with a somewhat smaller corolla and calyx, including the type of Convolvulus thomsonii , which is atypical in its relatively short calyx and corolla but is clearly an immature specimen of this taxon. This species appears to be frequent in the highlands of northern Malawi and southern Tanzania. It is very close to Convolvulus sagittatus but differs in the larger sepals, 9-11 mm in length and the tomentose indumentum, which dries brown. The rather long, often arching peduncles are also very characteristic. An unusual feature is the occasional presence of paired peduncles. It can be distinguished from Convolvulus aschersonii and Convolvulus austroafricanus by the larger solitary flowers as well as the tomentose indumentum. It is also close to Convolvulus galpinii differing principally in the longer, gradually narrowed sepals.

As with many other African species, intermediates with other species are found. These have the same indumentum, relatively large corollas and sepals of Convolvulus thomsonii but inflorescences of 2-3 flowers. Phillips 2738 and 3920 from northern Malawi and Richards 6071 from Zambia appear to be intermediate with Convolvulus austroafricanus or possibly Convolvulus aschersonii .