Solanum coagulans
Not known
Northeastern Africa with limited occurrence on the Arabian Peninsula; reported from Chad by Brundu & Camarda (2013); common weed of cultivated land, grazed ground, roadsides, coastal plains, and savanna; usually on sand, silt or loam; 0-1700 m elevation.
Solanum coagulans is a member of the Old World Clade within the Leptostemonum clade (Levin et al. 2006). With its close relaltive S. melastomoides, forms the Coagulans clade (Vronotsova et al. 2013)
Brundu, G., Camarda, I. 2013. The Flora of Chad: a checklist and brief analysis. PhytoKeys 23: 1-18. doi: 10.3897/phytokeys.23.4752
Friis, I. 2006. Solanum. In: M. Thulin (ed.), Flora of Somalia 3: 206-219. Royal Botanic Gardens, Kew, United Kingdom.
Jaeger, P.-M.L. 1985. Systematic studies in the genus Solanum in Africa. PhD thesis, University of Birmingham, United Kingdom.
Hepper, F.N. & Friis, I. 1994. The plants of Pehr Forsskal's Flora Aegyptiaco-Arabica: collected on the Royal Danish expedition to Egypt and the Yemen 1761-63. Royal Botanic Gardens, Kew, United Kingdom in association with the Botanical Museum, Copenhagen, Denmark.
Levin, R.A., N.R. Myers, & L. Bohs 2006. Phylogenetic relationships among the "spiny" solanums (Solanum subgenus Leptostemonum). Amer. J. Bot. 93: 157-169.
Vorontsova, M. S., and S. Knapp. 2012. Solanum spp. 26-45, 52-62, 65-66. In: J.M. Edmonds, Solanaceae, Flora of Tropical East Africa. Kew: Royal Botanic Gardens, Kew.
Vorontsova, M. S., S. Stern, L. Bohs, and S. Knapp. 2013. African spiny Solanum (subgenus Leptostemonum, Solanaceae): a thorny phylogenetic tangle. Bot. J. Linn. Soc. 173: 176-193. doi:10.1111/boj.12053
Whalen, M.D. 1979. Taxonomy of Solanum section Androceras. Gentes Herb. 11: 359-426.
Uses. Medicinal; fruits used to coagulate milk (origin of specific epithet).
Solanum coagulans is a variable and ubiquitous weed immediately recognized by its densely spiny accrescent calyx covering most of the berry. The androecium is zygomorphic with one anther protruding 1.5-2 mm beyond the others, although this is often difficult to see in pressed specimens. After the pericarp dries out the lobe apices of the accrescent calyx fall off, leaving dry bright yellow fruit enclosed in what looks like a truncate calyx but is actually only the fused base of the calyx lobes. It has been reported as an annual with a long taproot (Madgwick 11) or a perennial with a creeping underground rootstock (i.e., stoloniferous) (Bogdan 4735). Vegetative characters can be ambiguous in the absence of fruiting material but features useful for identification include the straight pale yellow spines and the yellowish green leaf color on herbarium specimens.
Solanum coagulans and the rarer sympatric S. melastomoides form the zygomorphic-flowered Coagulans clade (Vortonsova et al. 2013) with one filament longer than the others and black seeds. Solanum coagulans can be easily distinguished from S. melastomoides by its accrescent armed calyx (versus unarmed calyx with the lobes not markedly elongating in S. melastomoides), the long stamen exceeding the shorter stamens by 1.5-2 mm (versus 4-6 mm in S. melastomoides), mature leaves over 5 cm long with more than 3 lobes on each side (versus leaves under 5 cm long, entire or with up to 3 lobes in S. melastomoides).
Whalen (1984) and Jaeger (1985) note that the name S. coagulans has been commonly misapplied, and Whalen suggested that the name should be rejected on these grounds. It is now in common use for this species, so this is no longer a sensible option.