Begonia poilanei Kiew, 2007

Kiew, Ruth, 2007, Notes on Vietnamese Begonia (Begoniaceae), including three new species, Adansonia (3) 29 (2), pp. 229-238 : 235-238

Begonia poilanei Kiew , sp. nov.

( Fig. 2 )

A Begonia sinuata Wall. ex Meisn. pilis uniseratis (nec stellatis) recedit. Sect. Diploclinium

TYPUS. — Vietnam, Haut Donai District , Djijuih, 21.X.1931, Poilane 19824 (holo-, P barcode P00539147 ; iso-, P barcode P00539160 , barcode P00539161 ) .

DESCRIPTION

Herb stemless or with a short stem 1.5-3 mm long; basal tuber cylindric 1.5-2.5 cm long and 5-7.5 mm

thick, covered in a network of fibrous roots. Leaves one per plant, sometimes two, not oblique; petioles densely hairy when young, 6.5-12 cm long, slender to 2 mm diam. in the dried state; laminas symmetric, broadly ovate, 6.5-14.5 × 7-17 cm, in the dried state with a conspicuous reddish band c. 3-5 mm wide along the secondary and tertiary veins, with scattered uniseriate hairs 0.75-1 mm long, thinly papery in the dried state, base equal, cordate, sinus wide, basal lobes 1.75-4 cm long, margin denticulate and ciliate, apex shortly acuminate, acumen to 7.5 mm long, venation palmate with 4 pairs of veins, tertiary veins conspicuous and perpendicular or at 45° to the secondary veins, on the lower surface secondary veins with uniseriate hairs c. 3-4 mm long and even the smallest veins with hairs 1-1.5 mm long, in the dried state veins slightly impressed above and slightly prominent beneath. Flowers not known. Infructescences axillary, cymose panicles, erect, above the leaves, 12-26 cm long, peduncles 11.5-23 cm long, branching 3 or 4 times, distally with up to 4 fruits. Bract pair ovate, c. 2 × 1 mm, persistent. Fruits with slender hair-like pedicels 12-14 mm long, capsules 6-12 × 16-23 mm, glabrous, wings 3, unequal, thinly fibrous, dehiscing between the locules and wings, longer wing 10-13 mm wide, slightly falcate and tapering to a point, smaller two wings rounded, sometimes broadly acute, 4-5 mm wide, locules 3, placentas 2 per locule, styles 3, free to base, bifid, branches lyre-shaped and spirally twisted, 1.5-2 mm long, persistent. Seeds broadly barrelshaped, c. 0.25 mm long, collar cells c. ¾ of the seed length.

REMARKS

As Poilane noted on the herbarium label, this is a very pretty plant (“très jolie”) with foliage as attractive as any in cultivation. He described the leaves as tawny brown along the veins against a green background and being darker green beneath, the peduncles are sable yellow with flowers varying from pale to bright pink.

Very few Asian begonias have symmetric, nonoblique leaves. The only one in Vietnam is Begonia sinuata Wall. ex Meisn. , which in common with this new species is stemless or has only a very short stem and produces one or two broadly ovate leaves, a basal tuber, and fruits with three unequal wings. Begonia poilanei differs from B. sinuata in its larger leaves with a cordate base and in its uniseriate hairs. In contrast, B. sinuata has leaves up to 8 × 8 cm with a rounded or truncate base and its hairs are stellate. Among Vietnamese begonias, stellate hairs are unique to B. sinuata . Begonia sinuata belongs to sect. Parvibegonia and has ovaries with two locules each with two placentas.

Begonia harmandii Gagnep. is also similar in habit in that it is stemless and has tubers and sometimes has only one leaf. However, it differs in its oblique leaf that is longer than wide, its inflorescences that are racemose and its fruits with three equal, hairy, rounded wings. It is placed in sect. Reichenheimia on account of its single placenta per locule.

Begonia poilanei that has a three-locular ovary with two placentas per locule belongs to sect. Diploclinium and conforms to the Doorenbos et al. (1998) Group III of this section in the plant being tuberous, having a reduced stem with one or two symmetric leaves, an axillary inflorescence and styles persisting in the fruit. Begonia cavaleriei H.Lév. is the only other Vietnamese begonia in this section but it differs in having peltate leaves.

Two specimens, one from Cambodia (Martin M244, P, sterile) and the other from Thailand (Larsen et al. 1003, P, with male and female flowers) are very similar to B. poilanei in having one symmetric ovate leaf with the same dimensions, coloration and indumentum. They differ in that both these specimens have leaves with the base without a wide sinus, the margin being deeply serrate, the apex strongly acuminate with an acumen to 2 cm long, and the venation being palmate-pinnate. The fertile Thai specimen has a similar inflorescence and ovary, the latter with unequal, thinly fibrous wings, the longer one being slightly falcate, and with three styles with lyre-shaped branches. However, the Thai specimen has one placenta per locule, which would place it in sect. Reichenheimia ; in contrast, B. poilanei , has two placentas per locule and so belongs to sect. Diploclinium (though one placenta may be poorly developed). Until more material from these three countries is available, it is uncertain whether they belong to one or two taxa. Presently, B. poilanei is known from a single fruiting specimen.

This new species is named in honour of M. Poilane, who discovered and collected this beautiful begonia, in recognition of his extensive contribution to botanical collecting in Vietnam

(more than 40 000 specimens).

DISTRIBUTION

Endemic in Vietnam, Haut Donai District , Djijuih (Dalat). Known only from the type .

HABITAT

At 250 m altitude, growing on bare, vertical rock surfaces.

Figures

FIG. 2. — Begonia poilanei Kiew: A, habit; B, fruit with persistent stigmas; C, transverse section of fruit. Poilane 19824. Scale bars: A, 15 mm; B, 3 mm; C, 2 mm.