The Spermacoce of the Australia

Harwood, Aust. Syst. Bot. 18: 339, 2005.

Type: West of Wildman River Ranger Station, NT, 13.iii.2001, R.K. Harwood 1034; holo: DNA; iso: BR, BRI, CANB, K, L, MEL, PERTH, SI.

Annual or perennial herb, prostrate, to c. 50 cm across or more rarely spreading and then to 30 cm tall; stems ribbed, moderately to densely hairy. Leaf blades narrowly ovate or narrowly elliptic, rarely ovate, 12–70 x 3–19 mm, acute at the apex, cuneate at the base, glabrous at both sides or scabrous to shortly hairy adaxially and on the veins abaxially; mid-vein somewhat prominent abaxially; secondary veins visible or not, never very prominent; margins not callused. Stipules fimbriate; base 1-3.5, hairy; fimbriae 3-9, to 3(-5) mm long, often hairy. Flowers subsessile in many-flowered capitula; capitula terminal, to 25 mm wide, subtended by one or rarely two pairs of leaves; subtending leaves often broader at the base than other leaves and sometimes partially red-brown; bracts stipuliform with setae to 4 mm long. Calyx tube to 1 mm; lobes 4, green with a white or blue margin, narrowly triangular to linear, to 7 mm long but often much shorter, glabrous or scabrous to shortly hairy on the margins, often scaberulous at the apex. Corolla white to blue; tube narrowly cylindrical, 1.6-7.2 mm long, glabrous outside, with moniliform trichomes for most of its length inside; lobes oblong to narrowly oblong, erect except for spreading tips, 1.2-2.8 mm long, with scattered trichomes particularly towards the apex outside, with a row of trichomes along the mid-vein below appendages inside; appendages converging to mid-vein and then partly running together, continuous for most of their height. Stamens exserted, not exceeding top of appendages, inserted at corolla tube apex; anthers elliptic, 0.7-0.9 mm long; filaments 0.8-2 mm long. Style exceeding erect part of corolla lobes, 2.8-9.3 mm long; stigma appearing capitate or shortly bilobed; nectary disc entire, slightly raised, glabrous. Capsule obovate-elliptic or widely obovate-elliptic, 1.3-2.6 x 1.1-2.4, hairy towards apex; septum lamellas partly remaining attached to the valves at dehiscence. Seeds brown, elliptic or oblong, 1.1-2.05 x 0.5-0.9 mm; testa surface faintly reticulate, mostly appearing smooth; ventral groove c. 1/2 of width of seed, not extending under testa margin; obturator persistent along full length of ventral groove, membranous, the sides erect or inclined towards the groove margin.

Distribution Map
NT and QLD: occurs throughout the Top End east from Katherine and the Mary River near Darwin and south-east up to settlement creek, just over the Queensland border.

Habitat and phenology
Occurs in woodlands on sandy or loamy soil, often with gravel present, on flats or in sandstone hills. Flowering and fruiting from December to July.

Notes
S. fabiformis is close to S. brevicilia, S. erosa and S. stigmatosa, three species endemic to the Northern Territory. Differences between the four species are given by Harwood & Dessein 2005.
Three collections from Groote Eylandt have much longer calyx lobes and corollas.

Etymology
Latin fabiformis (bean-shaped), referring to the distinct shape of the seeds.

Selected specimens (55 examined)
NORTHERN TERRITORY: Groote Eylandt; 7 km SE Alyangula, 11.iv.1992, I.D. Cowie 2532 (BRI, DNA); North of Maningrida, 8.iv.2000, R.K. Harwood 822 (AD, BR, BRI, CANB, DNA, K, L); North Island, Pellew group, 7.iii.2000, R.K. Harwood 837 (BR, BRI, DNA, K, PERTH); Stuart Highway, 28 km N of Katherine, 28.iv.2000, R.K. Harwood 851 (BR, BRI, CANB, DNA, K, PERTH, SI); Cadell River Gardens, 25.vi.1972, J. Must 1064 (CANB, DNA, K, L). QUEENSLAND: Settlement Creek, ii.1923, L. Brass 290 (BRI).