Solanum mammosum L.

A weedy shrub of grasslands, pastures, roadsides, waste places, secondary growth and cultivated land in warm tropical areas with at least seasonally heavy precipitation, mostly from sea level to 100 m elevation but reaching at least 1800 m. Flowering and fruiting throughout the year with no trends apparent. Confined entirely to the tropics, native in northern South America and possibly the Caribbean; common on the Caribbean islands; in Central America from southern Mexico to Panama and in an arc around the Amazon basin from northwestern Bolivia to the Guyanas, rare and sporadic in the Amazon valley and east coast of Brazil. Sporadically introduced elsewhere; rare in Africa, more common in the East Indies. As an ornamental plant and curiosity it can be expected to be cultivated anywhere in the tropics and has the potential to escape; the label data of many of the older specimens are not explicit on the status of the plants.

Solanum mammosum can be distinguished from other species in section Acanthophora by the combination of its purple corollas, long copious pubescence, and its usually bizarre nipple-shaped fruit. It is most similar to S. palinacanthum, which also has purple corollas, but which has short glandular puberulence and exclusively globose fruits.The morphological and geographical reasons for considering this species native to northern South America and possibly the Caribbean have been discussed previously (Nee, 1979). Briefly, the globose fruit form is undoubtedly the primitive condition and is nearly confined to the Llanos of Venezuela and adjacent areas where the species seems well-adapted to the seasonally dry grassland climate. It is only rare and sporadic in Brazil south of the Amazon basin, the center of diversity of the section. Because of the widely acknowledged utility of its poisonous fruits in killing rats and cockroaches, it has been to a minor extent cultivated and spread. The elongated apical nipple probably arose before it was spread, probably by pre-Columbian Indians, to the Caribbean islands. Sometimes later arose a mutation for the abnormal proliferation of five style-like protrusions from the base of the ovary. These plants have been propagated as a curiosity, being certainly the most bizarre in the whole Solanaceae. Selection for less spiny plants has also occurred.

Guangdong, Guangxi, Yunnan [native to South America].

Habit

Shrubs 0.5–2 m tall, with single stem usually becoming branched soon above the base, often flowering while still herbaceous. Stems to 4 cm in diameter at base, terete, green or purple tinged, densely soft spreading pilose with simple 3–5-celled simple hyaline hairs 2–3.2 mm long interspersed with ca. 0.2 mm long simple gland-tipped hairs; stem prickles usually sparse to many, viciously sharp, straight or usually recurved, mostly greater than 5 mm long, up to 20 mm long, from greatly enlarged and compressed bases up to 10 mm wide, minutely stipitate-glandular, and with simple hairs shorter than those of stem, rarely unarmed.

Sympodial Structure

Sympodial units 2-foliate, usually geminate.

Leaves

Leaves simple, if geminate then one about twice the size of the other, the major blades 8–17 x 9–20 cm, suborbicular, thin-textured, adaxially soft-pilose with 3–5-celled simple hyaline hairs 1.4–1.8 mm long and glandular with 1–2-celled gland-tipped hairs 0.2–0.5 mm long, glandular-puberulent abaxially with 1–2-celled gland-tipped hairs 0.2–0.5 mm long, soft-pilose with 3–5-celled simple hyaline hairs 1.4–1.8 mm long and with many sessile 3–7-rayed stellae with 0.15–0.6 mm long basal rays at a ca. 45? angle, the central ray elongate, ca. 3-celled, 1.2–2.2 mm long; armed adaxially and abaxially with straight spreading prickles similar to those of the petiole and grading in size from those of largest petiole prickles on the major veins to minute ones on smaller veins; base cordate; margin parted 1/4 to 1/2 way to the midrib with usually 2 pairs of main lobes, the lobes with additional acute triangular lobes or coarse teeth; apex acute; petioles of the larger leaves 5–12 cm, soft spreading pilose with hairs like those of stem, with (0–) 2–8 stout evenly tapering straight spreading prickles 0.5–2.5 cm long with compressed bases up to 0.5 mm wide and minute stipitate glands and short simple hairs concentrated near the base.

Inflorescences

Inflorescences sessile, extra-axillary, unbranched, with 2–10 flowers, usually only the lowermost flower fertile, occasionally two and exceptionally up to 5 fruits developing, the axes pilose like the stem, unarmed or with a few small straight spreading acicular prickles less than 5 mm long; peduncle absent; rachis to 2 cm long; pedicels 10–20 mm in flower, those of fertile flowers soon strongly curved, 15–30 mm in fruit, curving around the stem with fruit held ± perpendicular to the stem, nearly contiguous, the male flowers articulated at the base.

Flowers

Flowers with the calyx 5–8 mm long, the tube 1–1.5 mm, the lobes 3–5.3 long, 1–2 mm wide at the base, narrowly lanceolate, almost linear, spreading-pilose with 2–5-celled simple hyaline hairs to 2.5 mm long and much shorter 1–2-celled simple gland-tipped hairs ca. 1.2–1.6 mm long, unarmed or with a few straight acicular prickles less than 5 mm long; fruiting calyx expanding to ca. 10 x 4 mm at the base, then shrivelling and usually irregularly falling in the mature or senescent fruit. Corollas 1–2 cm in diameter, stellate, thin-textured, blue-purple, the tube 3–4 mm, the lobes 13–15 x 2–3 mm, narrowly triangular, spreading-pilose abaxially with 3–6-celled simple hyaline hairs 0.8–3.2 mm long and glandular with 1–2-celled gland-tipped hairs up to 0.4 mm long. Stamens with relatively stout filaments 1–1.2 mm; anthers 8–12.5 long, 2–2.2 mm wide at the bae, the tips narrowed and somewhat curved, the pores small and directed apically. Ovary with minute stipitate glands ca. 0.05 mm long; rudimentary styles ca. 1.2–2.0 mm long; fertile styles ca. 12 x 0.5 mm, exceeding the anther column by ca. 2.2 mm; stigma 0.8 mm wide, 0.4 mm long, capitate, abruptly expanded, slightly bilobed.

Fruits

Fruits 3.5–5.5 cm in diameter, sometimes globose or depressed-globose, usually narrowed abruptly or gradually to a cylindrical apical "nipple" up to 2 x 2.5 cm, and then the whole fruit 4–8 cm long, often with (1–) 5 cylindrical or ovoid basal lobes to 2 cm in diameter and 3 cm long, bright yellow or orange-yellow, becoming darker and duller orange in senescence; exocarp shiny, tough, glabrous; mesocarp spongy, white, ca. 7 mm thick; seed cavity globose, ca. 2.5 cm in diameter.

Seeds

Seeds 3–3.5 x 4–4.5 mm, compressed, suborbicular, yellowish brown or brown, minutely foveolate, the surface nearly smooth, embedded in thin light greenish pulp.