Maesa angustibracteolata 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 : 246-248

Maesa angustibracteolata Sumanon & Utteridge , sp. nov. ( Fig. 1 )

Recognised in the genus Maesa by the following combination of characters: the scrambling habit, lacking hairs but with scales throughout, obovate leaves, simple to compound racemose inflorescences and pentamerous flowers with distinctive narrowly triangular bracteoles;

Type :— PAPUA NEW GUINEA. Central Province : Western Section , Tributary of Laloki River, 2 miles E of Rouna, 9°25’S, 147°19’E, elev. 1900 ft [c. 580 m], 11 September 1962, T. G. Hartley 10713 (holotype K!; isotypes CANB!, L image!) .

Scrambler. Indumentum: all parts lacking hairs, scaly on leaf lamina surfaces, inflorescences and fruits, scales peltate, up to 0.15 mm in diameter, pale ginger brown, ± sessile, circular with irregular margins. Branches drying reddish brown (chestnut) with scattered lenticels. Leaves: lamina obovate, 5.8–11.2 cm long, 3.8–6.0 cm wide, sub-coriaceous, drying dark brown above, reddish brown below, ad- and abaxial surfaces scaly; base obtuse to cuneate; margins entire; apex rounded to obtuse, sometimes emarginate; midrib glabrous adaxially and abaxially (scales absent); secondary veins 6 pairs, eucamptodromous, indumentum as lamina; petiole 1.7–2.5 cm long, glabrous. Staminate inflorescences and flowers not seen. Pistillate inflorescences terminal, solitary, racemose, simple or compound with 2–3 branches, 4–10 cm long in fruit, axis scaly. Pistillate flowers not seen, pentamerous (floral merosity determined from fruit morphology), bracts narrow triangular. Fruits globose, 3.5–3.7 mm long, 3.2–3.6 mm diameter, scaly, reddish brown; pedicels in fruit 2.3–2.9 mm long, densely scaly distally; bracteoles narrow triangular, 0.7–1.0 mm long, 0.2–0.3 mm wide, apex acute, margins entire, scaly, remaining ±opposite each other at the base of the fruit; calyx lobes overlapping, persistent.

Distribution and ecology:— The species is currently only known from Central Province in Papua New Guinea. It was recorded as liana or climber in rainforest on slopes from c. 580 m to c. 1280 m elevation.

Etymology:— The epithet refers to the distinct, narrowly triangular bracteoles.

Additional material examined:— PAPUA NEW GUINEA. Central Province : Boridi [9°5’S, 147°38’E], elev. c. 4000 ft [c. 1220 m], 22 October 1935 (fr.), C. E . Carr 14704 ( CANB!, K!, L image!); ibid., elev. c. 3500 ft [c. 1067 m], 22 October 1935 (fr.), C. E . Carr 14716 ( CANB!, K!, L image!); ibid., elev. 4200 ft [c. 1280 m], 7 November 1935 (fr.), C. E . Carr 14822 ( CANB!, L image!, NY!) .

Notes:— Maesa angustibracteolata is unique in the genus in having narrow triangular bracteoles and is thus easily distinguished from all other species in the genus. The combination of characters including the scrambling habit, obovate leaves, simple to compound racemose inflorescences with pentamerous flowers (the persistent calyx lobes on the fruit allow inferences of floral merosity), and lacking hairs but being scaly in most parts, makes this species distinctive.

From the key to the genus provided by Sleumer (1987), M. angustibracteolata would key out to M. haplobotrys because Sleumer did not make use of plant habit in the key - several of his taxa are morphologically heterogenous with regard to habit, something that is observable only during field studies, e.g., see the differences between the shrub species M. ruficaulis S. Moore (1916: 102) and the scrambling (‘climbing’) species M. rufovillosa detailed in Utteridge (2001: 680; 2013: 683). Maesa angustibracteolata is unlikely to be confused with M. haplobotrys , even though they share the same floral merosity and indumentum, with the habit being especially diagnostic ( M. angustibracteolata is a scrambling species; M. haplobotrys is a shrub/tree species), together with the leaf morphology ( M. angustibracteolata with obovate leaves with rounded to obtuse or sometimes emarginate apices; M. haplobotrys with elliptic–obovate leaves with acute apices), and inflorescence structure ( M. angustibracteolata with mostly compound racemes with 2–3 branches, occasionally simple, solitary in the leaf axils; M. haplobotrys with 1–3 simple racemes from the same axil).

Of the other scrambling Maesa species in New Guinea, M. angustibracteolata is most similar to M. loranthifolia Mez (1922: 125) , but differs from that species in the free bracteoles (bracteoles fused in M. loranthifolia ), compound racemose inflorescences with 2–3 branches (occasionally simple racemose) (simple racemose in M. loranthifolia ), obovate leaves with 6 pairs of secondary veins and a rounded to obtuse, or sometimes emarginate, apex (elliptic to obovate leaves with usually 4 pairs of secondary veins and a broadly acute apex in M. loranthifolia ).

The flowers were noted as being ‘dull brownish olive’ (fide Carr 14704) but no flowers were seen on the material examined, only hypanthia/young fruit.All species of Maesa have white corollas and we assume that Carr was referring to the infructescences and the developing fruits, rather than the flowers.

Figures

FIGURE 1. Maesa angustibracteolata Sumanon & Utteridge. A habit, plant in fruit; B node with petiole and inflorescence base; C leaf abaxial surface; D part of infructescence; E fruit apex; F LS of fruit; G scales on fruit surface; H scales on pedicel.All from Hartley 10713 (K). Scale bars: dashed bar = 0.5 mm, graduated single bar = 2 mm and 5 mm, double bar = 1 cm, graduated double bar = 5 cm. Illustration by Andrew Brown.