Solanum mitchellianum
Citation:
Repert. Spec. Nov. Regni Veg. 12: 131. 1913.
Type:
Australia. “Subtropical New Holland, anno 1846,” T. Mitchell s.n. (lectotype, K, designated by Symon, 1981; isolectotypes, BM, L).
Last edited by:
Bohs, L.
Written by:
A.R. Bean
Habit:
Erect, rhizomatous perennial shrub, 0.5-1.8 m tall. Stems green, terete or ridged, densely stellate-pubescent, the stellae 0.4-0.7 mm in diameter, the stalks 0-0.15 mm long, the lateral rays 6-8, porrect, the midpoints 0.5-1 times as long as lateral rays, eglandular; finger hairs absent; very short, gland-tipped hairs sparse; prickles straight, acicular, 1-10 mm long, 14-20 times longer than wide, with 240-1400 prickles per dm on juvenile branches, 240-1400 per decimetre on adult branches.
Sympodial structure:
Sympodial units apparently 2-foliate, not geminate.
Leaves:
Leaves simple, the blades 5.5-11.5 x 1.8-8 cm, chartaceous, the juvenile leaves with blades ca. 11.5 x 8 cm, ovate, deeply lobed, with 3-4 pairs of lobes, with ca. 40 prickles on upper surface, the adult leaves with blades 5.5-10.5 x 1.8-6.5 cm, 1.5-3 times as long as wide, ovate, green and very sparsely to moderately stellate-pubescent adaxially, the hairs distributed throughout, spaced 1-3 mm apart, 0.25-0.7 mm across, the stalks 0-0.1 mm long, the lateral rays 4-8, porrect, the midpoints 0.8-1.5 times as long as lateral rays, eglandular; finger hairs absent; very short, gland-tipped hairs present only in vein depressions; prickles present on midvein and lateral veins, 8-20, straight, acicular, 1-8 mm long; white and very densely stellate-pubescent abaxially, the hairs spaced ca. 0.05 mm apart, 0.5-0.8 mm in diameter, the stalks 0-0.3 mm long, the lateral rays 7-9, porrect, the midpoints 1-1.5 times as long as lateral rays, eglandular; finger hairs absent; very short, gland-tipped hairs absent; prickles present on midvein only or present on midvein and lateral veins, 2-10, straight, acicular; base obtuse or cordate, oblique part 0-3.5 mm long; margin entire or shallowly lobed throughout, the lobes 3-4 on each side, acute or obtuse, lobing index 1-1.9; apex acute; petioles 1.1-2.8 cm long, 18-30% length of lamina, densely stellate-pubescent, prickles present.
Inflorescences:
Inflorescence extra-axillary, unbranched or 2-3-branched, with 7-25 flowers, all flowers perfect, the axes armed; peduncle 2.1-4 cm; pedicels 3-6 mm long in flower, 0.3-0.6 mm thick at midpoint, the same thickness throughout or markedly thicker distally, 8-10 mm long in fruit, 0.8-0.9 mm thick at mid-point, articulated at the base.
Flowers:
Flowers homostylous, 5-merous. Calyx tube 0.5-1.5 mm long, the lobes 2-3.5 mm long, hemispherical, deltate, or attenuate, moderately to densely stellate-pubescent, the hairs transparent, 0.25-0.5 mm across, sessile, the lateral rays 5-8, the midpoints 0.8-1.2 times as long as lateral rays, eglandular; finger hairs absent; very short, gland-tipped hairs absent; prickles absent; fruiting calyx with lobes less than half length of mature fruit, unarmed. Corolla 7-10 mm long, stellate, chartaceous, purple, glabrous adaxially. Stamens with anthers 3.5-5.5 mm long, yellow, the pores minute and directed distally. Ovary glabrous or with stellate hairs only; style 6.5-8.5 mm long, glabrous or with stellate hairs only, the stellae ca. 0.4 mm across, the lateral rays ca. 8, the midpoints ca. 1 times as long as lateral rays.
Fruits:
Fruits 7-17 per inflorescence, 0.8-0.9 cm in diameter, 1-locular (septum absent or incomplete), globose, black, glabrous, the exocarp 0.1-0.2 mm thick, the mesocarp juicy, succulent, the placenta not apparent.
Seeds:
Seeds 1.8-2.4 mm long, brown to black.
Chromosome number:
Not known
Distribution:
Solanum mitchellianum extends from Springsure and Blackwater in Queensland to Warialda in New South Wales, Australia. It inhabits semi-evergreen vine thickets, brigalow-belah communities or shrubby eucalypt woodlands often with rock outcrops.
Phenology:
Flowers are recorded for all months of the year; mature fruits are recorded between September and April.
Phylogeny:
Solanum mitchellianum is a typical member of Solanum subgenus Leptostemonum. It is placed into the S. semiarmatum group (Group 13A) by Bean (2004) on morphological grounds; its phylogenetic position has not been investigated using molecular data.
References:
Symon, D.E. 1981. A revision of Solanum in Australia.
J. Adelaide Bot. Gard. 4: 1-367.
Bean, A.R. 2004. The taxonomy and ecology of Solanum subg. Leptostemonum (Dunal) Bitter (Solanaceae) in Queensland and far north-eastern New South Wales.
Austrobaileya 6 (4): 639-816.
Solanum mitchellianum is closely related to S. semiarmatum, and for many years included in synonymy with it (Symon, 1981). Solanum mitchellianum is however amply different by virtue of the shallowly lobed or entire adult leaves, stellae on the lower leaf surface sessile or with stalks <0.3 mm long, ovary glabrous or with stellae only (with very short, gland-tipped hairs only for S. semiarmatum), styles glabrous or with stellae (with very short, gland-tipped hairs only for S. semiarmatum), and calyx prickles absent (present for S. semiarmatum).
Solanum mitchellianum is also apparently closely related to S. coracinum. Solanum coracinum differs by the glabrous to sparsely pubescent branchlets and leaf undersides, the deeply lobed leaves with more prickles on the upper surface, and the stellae of the lower leaf surface with a shorter central ray. Three specimens (Bean 17776, Thomby Range; Beasley s.n., Chinchilla; and Fensham 2877, NNW of Miles) appear to represent intergrades between it and S. mitchellianum. Solanum mitchellianum occurs to the east, west and north of the geographical range of S. coracinum.
Conservation status: Widespread. Not considered at risk.