Oxygonum annuum S.Ortiz & Paiva

Flora Zambesiaca. Vol. 9, Part 3. Polygonaceae-Myriaceae. Pope GV, Polhill RM, Martins ES. 2006.

Habit

An erect annual herb An erect annual herb.

Stem

Stems branching at the base and laxly above, angular-striate, greenish, reddish at the base, with simple white hairs at the base and to a varying extent above Stems branching at the base and laxly above, angular-striate, greenish, reddish at the base, with simple white hairs at the base and to a varying extent above.

Leaves

Leaves greenish, (8)20–30(60) × 0.3–0.7(1) mm, narrowly linear, glabrous or with simple white hairs Leaves greenish, (8)20–30(60) × 0.3–0.7(1) mm, narrowly linear, glabrous or with simple white hairs.

Ocrea

Ocrea (4)5–6(9) mm long, often 3–4 dentate at the apex, surface glabrous or somewhat pubescent, apex glabrous or with a fringe of c. 0.2 mm long hairs Ocrea (4)5–6(9) mm long, often 3–4 dentate at the apex, surface glabrous or somewhat pubescent, apex glabrous or with a fringe of c. 0.2 mm long hairs.

Flowers

Hermaphrodite flowers homostylous or not conspicuously heterostylous; perianth 5-lobed; tube 0.5–1 mm long, pubescent; lobes 1–2(2.5) mm long, white, tinged with pink at the abaxial surface, sometimes pubescent Male flowers not seen Flowers pedicellate, 3(4) in the axils of bracts, 1(2) flowering at a time, arranged in terminal spiciform, slender racemes up to 21 cm long; bracts up to 5 mm long, truncate, sometimes with a acuminate apex up to 1 mm long, glabrous to pubescent, with short apical cilia; pedicels erect, up to 5 mm long, filiform Flowers pedicellate, 3(4) in the axils of bracts, 1(2) flowering at a time, arranged in terminal spiciform, slender racemes up to 21 cm long; bracts up to 5 mm long, truncate, sometimes with a acuminate apex up to 1 mm long, glabrous to pubescent, with short apical cilia; pedicels erect, up to 5 mm long, filiform. Hermaphrodite flowers homostylous or not conspicuously heterostylous; perianth 5-lobed; tube 0.5–1 mm long, pubescent; lobes 1–2(2.5) mm long, white, tinged with pink at the abaxial surface, sometimes pubescent. Male flowers not seen.

Filaments

Filaments 0.5–1.5 mm long; anthers 0.5–0.7 mm long

Ovary

Ovary c. 1 mm long; styles c. 1.5 mm long

Ecology

Sandy roadsides, Guibourtia and Baikiaea woodland, Kalahari Sand; c. 1000–1100 m.

Note

The most similar species to O. annuum is O. lineare De Wild., from Dem. Rep. Congo and Angola, which likewise has linear leaves and ellipsoid fruits; however this species can be easily differentiated from O. annuum since it often has stems glabrous at the base, wider leaves ((0.5)1–2.3(9) mm) that are linear to elliptic, more flowers per bract ((4)6–14), the entire corolla always glabrous, longer corolla lobes (2.5–3(3.5) mm), wider fruits (2.5–3(3.5) mm), markedly heterostylous flowers and fruits without transverse wrinkles.

Distribution

ZAM B, ZAM W Zambia Also in Angola.

Male

Male flowers not seen.

Stamens

Filaments 0.5–1.5 mm long; anthers 0.5–0.7 mm long.

Pistil

Ovary c. 1 mm long; styles c. 1.5 mm long.

Hermaphrodite

Ovary c. 1 mm long; styles c. 1.5 mm long. Filaments 0.5–1.5 mm long; anthers 0.5–0.7 mm long. Hermaphrodite flowers homostylous or not conspicuously heterostylous; perianth 5-lobed; tube 0.5–1 mm long, pubescent; lobes 1–2(2.5) mm long, white, tinged with pink at the abaxial surface, sometimes pubescent.

Fruits

Nut 4–5 × 2.3–2.5 mm, ellipsoid, with c. 12 longitudinal ridges and numerous transverse wrinkles, glabrous or pubescent. Nut 4–5 × 2.3–2.5 mm, ellipsoid, with c. 12 longitudinal ridges and numerous transverse wrinkles, glabrous or pubescent.