Lasianthus constrictus Wight

Zhu, H., Roos, M. C. & Ridsdale, C. E., 2012, A taxonomic revision of the Malesian species of Lasianthus (Rubiaceae), Blumea 57 (1), pp. 1-102 : 30

29. Lasianthus constrictus Wight

Lasianthus constrictus Wight (1846) 515; Kurz (1877) 31; Hook.f. (1880) 188; King & Gamble (1904) 117;Merr.(1921) 577;Ridl. (1923a) 163; Craib (1934) 209; Bakh.f. (1965) 342; K.M. Wong (1989) 369; H.Zhu (2001b) 124. —

Type: Griffith s.n. (holo K), Burma .

Lasianthus constrictus Wight var. latifolius Craib (1934) 209. — Type: Kerr 14940 (holo K; iso BK), Thailand. Pattani.

Shrubs; branchlets thinly appressed-pubescent. Leaves: blades lanceolate to oblong-lanceolate, 8–13 by 3–4 cm, subcoria- ceous, yellowish brown when dry, glabrous above, sparsely strigose on nerves beneath, apex acute to shortly caudate or acuminate, base acute; midrib, nerves and nervules prominent on both surfaces, nerves 3 –6 pairs, nervules subreticulate; petioles 4–5 mm long, sparsely strigose. Stipules small, triangular, 3–4 mm long, sparsely strigose. Cymes sessile or subsessile; bracts absent. Flowers sessile, small, crowded; calyx with an obconical tube and a hemispherical limb, minutely strigose, somewhat constricted at the throat, tube 1.5– 2 mm long, limb shortly 4-toothed or almost truncate, c. 1 mm long; corolla hirsute or glabrous outside, tube about 3 mm long, lobes c. 2 mm long. Drupes ovoid or ellipsoid, with a constricted base, glabrous, crowned by a cupular calyx-limb which is somewhat constricted at base; pyrenes 2–4, very furrowed on the abaxial face.

Distribution — Burma, Thailand (Peninsular), Singapore, Malaysia ( Sarawak, Sabah), Brunei, Indonesia (Sumatra, Java, Kalimantan).

Notes — Var. latifolius differs from the typical variety by having broader leaves. However, the demarcation becomes vague when more specimens are checked and var. latifolius cannot be clearly separated from var. constrictus .

This species has a calyx constricted at base of cupular limb and drupes crowned by calyx limb constricted at base with 2–4 developed pyrenes. The same type of drupes is found in L. reticulatus (= L. maingayi ). Lasianthus constrictus is very closely related to L. reticulatus . It differs from L. reticulatus by having relatively small leaves with 3– 5 pairs of nerves and subglabrous or sparsely strigose branches and leaf nerves beneath, shorter petioles, cymes usually sessile, calyx limb truncate or minutely toothed, while L. reticulatus has appressed-pubescent hairs on branches and nerves beneath, leaves relatively large with 6–7 pairs of nerves which are strongly prominent beneath, flowers sessile clustered in very short congested peduncles, calyx limb with 4 minutely triangular lobes.