Maesa pusilliflora Sumanon & Utteridge, 2021

Sumanon, Pirada, Eiserhardt, Wolf L., Balslev, Henrik & Utteridge, Timothy M. A., 2021, Six new species of Maesa (Primulaceae) from Papua New Guinea, Phytotaxa 505 (3), pp. 245-261 : 255-256

Maesa pusilliflora Sumanon & Utteridge , sp. nov. ( Fig. 5 )

Recognised in the genus Maesa by the combination of the following characters: obovate to oblanceolate leaves, entire leaf margins, pentamerous flowers, non-overlapping triangular calyx lobes, long hypanthium (more than 0.6 mm long), simple racemes, solitary or fasciculate with more than 15 flowers per inflorescence, and the flowers with non-overlapping triangular calyx lobes and the hypanthium 0.7–1.00 mm long.

Type:— PAPUA NEW GUINEA. Morobe Province: near Ilauru, basin of the upper Bulolo River [7°7’S, 146°36’E], elev. 1005.4 m, 19 August 1989 (fl.), W. Takeuchi 4645 (holotype BISH!; isotypes A!, K!, L image!) .

Small treelet. Indumentum: all parts lacking hairs, scaly on lamina surfaces, buds, inflorescences and fruits; scales peltate, up to 0.04–0.10 mm in diameter, cream–ginger, ± sessile, circular with irregular margins. Branches drying grey-brown with scattered lenticels, glabrous, scaly to densely scaly on young parts. Leaves: lamina obovate, 4.9– 7.0 cm long, 2.9–4.1 cm wide, sub-coriaceous, drying dark olive green above, tawny-brown below, adaxial surface glabrous, scaly when young, abaxial surface glabrous; base cuneate; margins entire; apex obtuse or sometimes acute; midrib drying reddish brown, glabrous both adaxially and abaxially; secondary veins 6–8 pairs, semicraspedodromous, indumentum as lamina; petiole 0.9–1.1 cm long, glabrous. Staminate inflorescences and flowers not seen. Pistillate inflorescences lateral (axillary), racemes, solitary or fasciculate with up to 3 inflorescences per axil, 4–5 cm long at anthesis, c. 5.5 cm long in fruit, axis sparsely scaly; pedicels 1.5–3.0 mm long, scaly distally; bracts ovate to triangular, 0.5–0.7 mm long, scaly to densely scaly, margins entire, apex acute; bracteoles ±opposite, inserted at the base of short elongated stalk of the hypanthium, shape as bracts, (0.45–) 0.6–0.7 (–0.9) mm long, 0.3–0.5 mm wide. Pistillate flowers pentamerous, drying whitish cream; calyx lobes triangular, 0.44–0.56 mm long, 0.5–0.9 mm wide, glabrous, margins entire to ciliate, apex acute; corolla tube c. 0.6 mm long, corolla lobes 0.44–0.7 mm long, 0.5–0.8 mm wide; hypanthium 0.7–1.0 mm long, scaly; ovary c. 0.4 mm long, 0.7–0.94 mm diameter, style 0.36–0.40 mm long. Fruits globose, 2.0– 2.6 mm long, 2.1–2.8 mm diameter, sparsely scaly; pedicels in fruit c. 2 mm long; bracteoles remaining ±opposite each other at the base of the fruit; calyx lobes non-overlapping, persistent.

Distribution and ecology:— This species is currently known only from the type specimen collected from Morobe Province, Papua New Guinea. The plant was found as a small treelet in burn-maintained rangeland with Cycas, Maotia , and Mussaenda shrubbery.

Etymology:— The epithet is derived from the Latin word ‘pusilli’ and the word ‘flora’ to refer to its tiny flowers; to be precise, whilst all species of the genus have small flowers, the corolla of this species is obviously smaller comparative to the hypanthium size.

Notes:— Maesa pusilliflora may be distinguished by the combination of characters outlined in the diagnosis. It is similar to M. beamanii , but it may be distinguished by floral merosity (pentamerous) and inflorescence structure (simple racemose with more than 15 flowers). This species is also similar to M. oblanceolatifolia , another new species from Milne Bay Province described in this paper; however, M. pusilliflora may be distinguished from M. oblanceolatifolia by the non-overlapping triangular calyx lobes and longer hypanthium (more than 0.6 mm long).

Figures

FIGURE 5. Maesa pusilliflora Sumanon & Utteridge. A habit (all leaves abaxial) with example of adaxial leaf surface to right; B node with petiole and base of inflorescence; C abaxial surface of leaf; D part of inflorescence; E pistillate flower, hydrated; F corolla opened flat; G LS of flower in E after removal of corolla; H fruit.A–G from Takeuchi 4645 (K), H from Takeuchi 4645 (BISH). Scale bars: single bar = 1 mm, graduated single bar = 5 mm (D) and 2 mm (H), double bar = 1 cm, graduated double bar = 5 cm. Illustration by Andrew Brown.