10. Solanum caesium Griseb., Abh. Königl. Ges. Wiss. Göttingen 24: 252. 1879.

Figs 32, 33

Solanum oranense Bitter, Repert. Spec. Nov. Regni Veg. 13: 170. 1914. Type. Argentina: Salta: Orán, Río de las Piedras, 3 Nov 1911, M. Lillo 10884 (lectotype, designated by Barboza et al. 2013, pg. 240: LIL [LIL001450]; isolectotypes: G, LIL [LIL001451], SI [051837, 075020]).

Type.

Argentina. Salta: Dpto. Orán, “Río, bei Oran ", 17 Oct 1873, P.G. Lorentz & G. Hieronymus 351 (lectotype, designated by Barboza et al. 2013, pg. 240: GOET [GOET003491]; isolectotypes: B, destroyed [F neg. 2766], CORD [CORD00006114], F [fragment of B duplicate, V0073222F, acc. # 621208], GOET [GOET003490, GOET003489]).

Description.

Large sprawling perennial herbs forming patches 1-2 m in diameter, the branches sometimes to several metres long. Stems strongly angled with wings ca. 1 mm wide, slightly fleshy and watery or rubbery, glabrous or with a mix of eglandular and glandular (only in Bolivia, see below) simple uniseriate trichomes, the eglandular trichomes 4-6-celled, ca. 0.5 mm long, the glandular trichomes denser, 4-6-celled, to 1.5 mm long, the terminal gland a single cell; new growth densely papillate and glabrous to moderately pubescent with simple uniseriate trichomes like those of the stems; older stems green or yellowish green. Sympodial units difoliate, the leaves not geminate. Leaves simple, often toothed, the blades (2.4)7-13 cm long, (1.7)2.5-8 cm wide, elliptic-ovate to narrowly elliptic-ovate, widest in the lower half, membranous to fleshy (watery), concolorous but with very distinct calcium oxalate inclusions in the mesophyll (crystal sand); adaxial surfaces glabrous or with a few glandular or eglandular trichomes to 1 mm long on the lamina; abaxial surfaces with the lamina glabrous or densely glandular-pubescent along the veins, the lamina densely papillate; principal veins 6-8 pairs, often forking distinctly before the margin, drying yellowish green, glabrous or densely pubescent with eglandular or glandular simple uniseriate trichomes; base attenuate onto the petiole and then onto the stem; margins entire or with a few large teeth (both can occur on the same stems), the teeth 1.1-2 mm long, 2-3 mm wide, broadly deltate with acute apices, the sinuses rounded, reaching ca. 1.3 of the way to the midrib; apex acute; petioles winged from the leaf base, 0.5-6 cm long. Inflorescences internodal, usually forked, but occasionally unbranched, (4)8-20 cm long, with 10-40 flowers borne along the branches, glabrous or sparsely pubescent with eglandular and glandular simple uniseriate trichomes like the stems; peduncle 2.5-10 cm long; pedicels 0.9-1.1 cm long, 0.5-0.75 mm in diameter at the base, 1.2-1.5 mm in diameter at the apex, fleshy and tapering, spreading at anthesis, glabrous or sparsely pubescent to densely pubescent with glandular simple uniseriate trichomes like those of the stems and leaves, articulated at the base leaving a distinct cup ca. 0.5 mm deep; pedicel scars ca. 2.5 mm apart. Buds ellipsoid, the corolla included within the calyx lobes until just before anthesis. Flowers 5-merous, cosexual (hermaphroditic). Calyx tube 1.5-2 mm long, conical; the lobes 2.5-4.5 mm long, 0.75-1 mm wide, long triangular and slightly narrower near the lobe base, often somewhat unequal in size, glabrous or sparsely glandular-pubescent with simple uniseriate trichomes to 1 mm long like the rest of the plant. Corolla 1.6-1.8(2) cm in diameter, white, rotate to shallowly stellate, lobed ca. 1/4 of the way to the base, the lobes 2.5-3 mm long, 3-5 mm wide, broadly deltate, reflexed to spreading at anthesis, adaxially glabrous, abaxially densely papillate and with a few longer simple uniseriate trichomes to 0.4 mm long. Stamens equal; filament tube to 0.5 mm long; free portion of the filaments 0.75-1.1 mm long, densely pubescent adaxially with tangled transparent simple uniseriate trichomes; anthers 3-4 mm long, 1-1.2 mm wide, ellipsoid, yellow, poricidal at the tips, the pores lengthening to slits with age. Ovary conical, glabrous; style 6-7 mm long, straight, exserted beyond the anther cone, densely papillate-pubescent in the lower half to 2/3; stigma capitate or bi-lobed and slightly heart-shaped, bright green in live plants, the surface minutely papillate. Fruit a globose berry, 0.5-0.8 cm in diameter, green when immature, becoming greenish orange when ripe, the pericarp thin, shiny, translucent when ripe, glabrous; fruiting pedicels 1.2-1.5 cm long, 0.5-0.6 mm in diameter at the base, 1-1.1 mm in diameter at the apex, fleshy, strongly deflexed and secund with a kink at the base, not persistent; fruiting calyx somewhat accrescent, the tube to 3 mm long, the lobes to ca. 6 mm long, ca. 2 mm wide, appressed to and enclosing the berry like a cage. Seeds more than 100 per berry, ca. 0.75 mm long, ca. 0.5 mm wide, not markedly flattened, teardrop shaped, pale yellow or creamy tan, the surfaces minutely pitted, the testal cells more or less rectangular in outline. Stone cells 2 at the apex of the berry, ca. 1 mm in diameter, cream-coloured, larger than the seeds but barely distinguishable in herbarium specimens. Chromosome number: not known.

Distribution

(Fig. 34). Solanum caesium is known from the eastern slopes of the Andes in Bolivia (Depts. Chuquisaca, Santa Cruz, Tarija) and Argentina (Provs. Jujuy, Salta).

Ecology and habitat.

Solanum caesium grows in wet forests and semi-deciduous forests, often in disturbed areas such as landslides, along roads and streams; from 400 to 2,100 m elevation.

Common names and uses.

Bolivia. Tarija: flor de oro (Coro-Rojas 1440). No uses recorded.

Preliminary conservation status

(IUCN 2022). Least Concern [LC]. EOO = 117,146 km2 [LC]; AOO = 184 km2 [EN]. Solanum caesium is widespread and common across its range and is a plant of disturbed areas. It occurs in protected areas in both Bolivia (Parque Nacional Serrania Aguarague) and Argentina (Parque Nacional Calilegua).

Discussion.

Solanum caesium is distinctive and not easily confused with any other morelloid in South America. The fleshy, almost succulent leaves that are usually glabrous, lax forked inflorescences with spaced flowers and reflexed pedicels that develop a distinct kink at the base in fruit, long-triangular calyx lobes that enclose the yellowish orange berry like a cage and the rotate corolla are all found in combination only in S. caesium. The fleshy leaves are similar to those of some populations of S. pentlandii, but that is a species of high elevations in Peru and Bolivia and has much smaller stellate flowers that are usually violet. It has been suggested (Del Vitto and Petenatti 1999) that S. caesium is related to the members of the Episarcophyllum clade; molecular sequence data (Gagnon et al. 2022) show this is not the case, but that S. caesium is a species of somewhat uncertain affinities.

Solanum caesium can form large plants and populations along open areas on roadsides and landslips. Plants throughout most of the species range are glabrous, except for populations from Santa Cruz (Bolivia) between Bermejo and Angostura where all plants seen have glandular pubescence (e.g., Wood 8652, Nee 35614, Cardenas 4636, Nee 35134, Wood 22538).