Solanum cordatum Forssk.

Solanum cordatum can usually be recognized by its long-filiform pedicels exceeding the leaves and membranous glaucous glabrescent leaves with long-decurrent narrowly-winged petioles. Unfortunately, neither of these characters is constant and it is important to look at the indumentum under the microscope; trichomes on the young stems of S. cordatum are compact and multangulate, with rays almost always under 0.1 mm long, and a small glandular tip is sometimes present on the midpoint of trichomes of stems, young leaves or both. The indumentum character is constant with the exception of a few collections from Somalia with longer-rayed stem trichomes. Label data records rooting easily on contact with the ground and at the nodes (Ellis 151, K, Collenette 5986, K) and fruit like cherry tomatoes (Wieland 4659, K); several collections from India and Pakistan record the flower color as white.

Solanum cordatum is frequently confused with the variable and largely sympatric S. forskalii. Solanum cordatum can be distinguished from S. forskalii by its multangulate trichomes with 12-18 rays under 0.15 mm long on the young stems (versus porrect trichomes with 6-10 rays over 0.15 mm long on the young stems of S. forskalii), 1-2 flowers per inflorescence (versus 1-20 flowers per inflorescence in S. forskalii), and anthers 3-5 mm long (versus anthers 4.5-7 mm long in S. forskalii). The two species occupy largely the same areas of northeastern Africa, the Arabian Peninsula, Pakistan, and India; S. forskalii is not known in Oman but occurs further west than S. cordatum in Egypt and Sudan. There is a clear morphological distinction between the two species in Saudi Arabia and Ethiopia, where S. forskalii has branched many-flowered inflorescences and dense indumentum. The separation is less clear in Somalia, Kenya and southern Arabian Peninsula; S. forskalii is more variable there with fewer flowers per inflorescence and smaller leaves. Carter & Stannard 583 from northern Kenya appears morphologically intermediate between the two species, with long-rayed porrect stem trichomes and anthers 7 mm long like S. forskalii but leaf morphology similar to S. cordatum. Solanum cordatum grows in grassland or open woodland, sheds foliage during drought and displays opportunistic growth in wet periods; S. forskalii grows in more open and rocky habitats, preserving water throughout the dry season with its dense indumentum cover and tougher tissue.

Solanum cordatum is similar to the rare Somalian endemic S. cymbalariifolium, and can be distinguished by its stellate-multangulate trichomes on the young stems (versus long simple trichomes visible with the naked eye on the young stems of S. cymbalariifolium), no prickles or prickles up to 4 mm long and more than 3 mm apart (versus dense filiform prickles 4-10 mm long and less than 0.5 mm apart on young stems in S. cymbalariifolium), and entire penninerved leaves (versus lobed leaves with 3-5 veins at the base of the leaf in S. cymbalariifolium).

Three duplicates of Deflers 488 are held in P and are potential lectotype material for S. sabaeorum; we have selected that with the best quality specimen (P00051784) as the lectotype.

Both S. obbiadense and S. nummularifolium were included as “S. n.” by Chiovenda (1925) in a key to Somali solanums, and although the descriptions are sufficient to make their publication valid, there were no specimens cited. We have neotypified both with only duplicates we have found of the single specimens cited by Chiovenda in his treatment of the same species in Flora somala (1929: 239, 240).