Solanum lapidosum A.R.Bean, 2012

Bean, A. R., 2012, A taxonomic revision of the Solanum echinatum group (Solanaceae), Phytotaxa 57 (1), pp. 33-50 : 39-41

Solanum lapidosum A.R.Bean , sp. nov. ( Fig. 2 , 6D )

S. rhaphiotes affinis sed indumento stellato sparso usque ad parce denso in pagina superiore folii, aculeis sparsis ramulorum (1–23 in quoque decimetro), radio centrali breviore pilorum stellatorum in partibus omnibus plantae, lobis calycis brevioribus et stylo excentrico differens.

Type: — AUSTRALIA. Northern Territory: 1.5 miles [2.4 km] SW of Cannon Hill, 2 February 1973, P. Martensz AE667 (holotype BRI!; isotypes CANB!, DNA! ).

Prostrate shrub 0.1–0.3 m high. Adult branchlets brown, grey or white; prickles 1–23 per decimetre, straight, acicular, 1–7 mm long, 6–10 times longer than wide, with scattered stellae near base; stellate hairs very dense, 0.3–0.4 mm in diameter, the stalks 0–0.1 mm long, the central ray 0.3–0.7 times as long as laterals. Adult leaves simple, the blades narrowly ovate to ovate, 3.6–10.2 cm long, 1.5–4.9 cm wide, 2.1–3.0 times longer than broad. Upper surface green or grey-green, prickles absent; stellate hairs sparse to moderate density, spaced 0.2–0.35 mm apart, 0.25–0.35 mm across, the stalks 0–0.1 mm long, the central ray 0.2–0.5 times as long as laterals. Lower surface white or grey, prickles absent; stellate hairs dense to very dense, spaced 0.05–0.15 mm apart, 0.4–0.5 mm diameter, the stalks 0–0.1 mm long, the central ray 0.2–0.5 times as long as laterals; entire or with 3–5 shallow obtuse lobes on each side, the base obtuse or auriculate, the oblique part 0–8 mm long, obliqueness index 0–8 percent, the apex acute; petioles 1.6–5.1 cm long, 33–78 % length of lamina, prickles present or absent. Inflorescence 2–5-flowered, with common peduncle 5–26 mm long, rachis prickles present; pedicels at anthesis 4–10 mm long, prickles absent; calyx tube 2–3 mm long, the lobes deltate, 0.5–1 mm long; calyx prickles absent or present at anthesis, 0–30 per flower, 0.5–2 mm long; calyx stellae very dense, yellow, 0.3–0.35 mm across, the stalks 0–0.1 mm long, the central ray 0.7–0.9 times as long as laterals. Corolla mauve or purple, 7–10 mm long, the inner surface glabrous; anthers 3.5–5.2 mm long; free part of the filaments 1.5–1.9 mm long; style ca. 10 mm long, strongly bent, eccentric, glabrous. Fruiting calyx almost closed at the apex rendering fruit almost invisible; stellate hairs all about the same size, stalks 0–0.1 mm long, proto-prickles absent; prickles>100, 2– 7 mm long, straight, with stellate hairs attached near the base; pedicels 10–13 mm long. Mature fruits 1–4 per inflorescence, oblate, 12–15 mm diameter.

Distribution and habitat: —Endemic to Kakadu National Park and adjacent parts of Arnhem Land in the Northern Territory ( Map 2 ). It grows on sandstone slopes, breakaways and outcrops, sometimes in crevices, or in sandy soil.

Phenology: —Flowers and fruits have been recorded from January to April.

Etymology: —From the Latin lapidosus, meaning ‘full of stones, stony’. This is a reference to the very stony habitat of this species.

Additonal specimens examined (paratypes): — AUSTRALIA. Northern Territory: 55 miles [89 km] E of Pine Creek, 29 January 1969, N. Byrnes NB1332 (DNA); Central part of Mt Brockman, 23 February 1973, L.A. Craven 2372 (DNA, CANB); Nourlangie Creek , 28 February 1973, L.A. Craven 2446 ( BRI, CANB, DNA); Little Nourlangie Rock, 19 March 1979, C.R. Dunlop 4763 (DNA); Little Nourlangie Rock, 20 March 1978, C.R. Dunlop 4777 (DNA); 42 miles [68 km] from Pine Creek , on El Sharana road, 12 January 1973, D.A. Hearne H391 (DNA); Mt Brockman Outlier , 15 km SE of Jabiru, 20 April 1989, R.W. Johnson 4744 ( BRI, DNA); Mt Brockman Outlier , 15 km SE of Jabiru, 20 April 1989, R.W. Johnson 4763 ( BRI, DNA); 2 km N of Nabarlek, 25 April 1979, M.O. Rankin 2203 ( CANB, DNA); Little Nourlangie Rock, Kakadu National Park , 20 April 1980, I.R. Telford 7797 ( CANB, DNA).

Notes: — Solanum lapidosum grows in the same general area as S. rhaphiotes , which is perhaps its closest relative. S. lapidosum differs from it by the sparse to moderate density of stellate hairs on the upper leaf surface, the sparser branchlet prickles (only 1–23 per decimetre), the shorter central ray of the stellate hairs on all plant parts, the shorter calyx lobes, and the eccentric style. It is not known whether these species ever occur together, but certainly there is no intergradation of these characters evident from herbarium material, and S. lapidosum can be instantly distinguished from S. rhaphiotes by the much sparser indumentum on the upper leaf surface.

Figures

FIGURE 2. Solanum lapidosum. A. branchlet and leaves; B. a stellate hair from the branchlet; C. corolla and stamens; D. calyx and pedicel at anthesis; E. ovary and style; F. fruiting calyx surrounding dried fruit; G. a section of the fruiting calyx showing prickles and hairs. A–B from Johnson 4763; C–E from Craven 2446; F from Telford 7797; G from Fox 431. Scale bar: A = 7.5 mm, B = 0.25 mm, C = 3 mm, D = 2 mm, E = 2 mm, F = 6 mm, G = 1 mm.

MAP 2. Distribution of Solanum fecundum (circles); Solanum lapidosum (triangles).

FIGURE 6. Solanum hair types. A. section of fruiting calyx of S. echinatum showing prickles and hairs; B. section of upper leaf surface of S. rhaphiotes; C. a stellate hair from S. lucani; D. section of upper leaf surface of S. lapidosum. A from Harris 432; B from Russell-Smith 556; C from Thompson WES122; D from Fox 431. Scale bar: A = 2 mm, B = 0.3 mm, C = 0.25 mm, D = 0.3 mm.