Begonia phamiana Kiew, 2007

Kiew, Ruth, 2007, Notes on Vietnamese Begonia (Begoniaceae), including three new species, Adansonia (3) 29 (2), pp. 229-238 : 232-234

3. Begonia phamiana Kiew , sp. nov.

Begonia rupicola auct . non Miq.: Gagnepain in Lecomte, Flore générale de l’Indo-Chine 2: 1106 (1921); Hô., Cây Cô Viêt Nam 1: 739, fig. 2055 (1991), Cây Cô Viêt Nam 1: 586, fig. 2341 (1999).

A Begonia geoffrayi Gagnep. foliis brevioribus angustioribus usque 11 × 5.5 cm (nec usque 18.5 × 10 cm) et alis fructus rotundato (nec acuto) differt. Sect. Parvibegonia.

TYPUS. — Cambodia, Île du Pic, Gulf of Cambodia 15.VIII.1905, Geoffray 483 (holo-, P barcode P00539153 ; iso-, P barcode P00539154 ) .

OTHER MATERIAL EXAMINED. — Vietnam. Île de Côn Dao, Germain 105 (P); Harmand 689 (P); Talmy (P).

DESCRIPTION

Glabrous herb with a stem 15-60 cm tall and 1-3 mm thick with internodes 3-6 cm long, pink, succulent, unbranched or shortly branched, with an ovoid tuber at the base. Stipules persistent, 7-12 mm long, apex acuminate. Leaves oblique; petioles grooved above, c. 3 cm long on the low- er leaves and c. 0.5 cm on the upper; laminas asymmetric, ovate, 10-16 × 4-7 cm, broad side 2.7-4.2 cm wide, basal lobe 1(-2) cm long, pale red beneath, in dried state thinly papery, base cordate, margin slightly crenate and rather sinuous, apex acuminate; venation palmate-pinnate with 1 or 2 pairs at the base and c. 4 pairs along the midrib and 1 or 2 veins in the basal lobe; in the dried state veins slightly prominent above and beneath. Inflorescences terminal or lateral on short branches, cymose panicles, 5-7 cm long, shorter than the leaves, lax, few-flowered, protandrous. Flowers pink of various shades. Male flowers with pedicel c. 7 mm long; tepals 4, outer two orbicular, 5-7 mm diam., inner two obovate, 5 × 3 mm; androphore c. 1 mm long, stamens many (c. 80-90), anthers narrowly lanceolate, apex slightly emarginate, 0.7 mm long and longer than the filaments, dehiscing through longitudinal slits. Female flowers with pedicels 7-10 mm long; tepals 6, the largest elliptic, c. 4 mm long, gradually decreasing in size to 2.5 mm long in the inner ones; ovary 3-winged, locules 2, placentas 2 per locule; styles short, joined for almost their entire length; stigmas cauliflower-like, distinctly bilobed. Fruits pendent with pedicels 10-12 mm long, capsules 9-10 × 11-15 mm; wings unequal, the long wing c. 8 mm wide, almost rectangular, apex obtuse; two shorter wings 2-3 mm wide.

REMARKS

The Vietnamese taxon is completely different from the Miquel’s Javanese species in being a much taller plant with a stem 20-60 cm long as opposed to about 15 cm long in Begonia rupicola and the leaves are larger and at least twice as long as wide (10-16 × 4-7 cm long) with a scarcely toothed margin whereas B. rupicola has smaller leaves that are as wide as long (7-8 × 8 cm) and the margin is distinctly toothed. Gagnepain’s taxon is a distinct new species that requires to be named.

This species is named in honour of Pham Hoang Hô. whose simple line drawings are an invaluable first step towards identifying Vietnamese begonias. Brummit & Powell (1992) assigned “P.H.Hô” as his authority name when in fact correctly it should have been H.H.Pham based on his family name, Pham – hence the species epithet. However, for the sake of consistency in the scientific literature, he is cited as Hô. in the text and as the scientific authority.

This group of succulent begonias in sect. Parvibegonia includes extremely variable species, which vary both within a lifetime and between populations ( Kiew [2005] has detailed this for Begonia integrifolia Dalziell and B. variabilis Ridl. in Malaysia). The Vietnamese species in this section do not appear to be either common or widespread. For example, B. integrifolia , a widespread species distributed from India to Peninsular Malaysia, in Vietnam is known only from Bà Ria-Vung Tâu, Mont Dinh (Pierre s.n., P), Ban Hoa, Mont Chua (Pierre s.n., P) and Île de Khon, Me Kong (Thorel s.n., P).

Begonia phamiana is readily distinguished from Vietnamese specimens of B. integrifolia , the other species in sect. Parvibegonia in Vietnam with asymmetric leaves, by its narrower laminas up to 11 × 5.5 cm (compared with broadly ovate laminas 6-7 × 6-6.5 cm in B. integrifolia ) and the attenuated leaf apex (compared with the broadly acute one in B. integrifolia ). It is in fact more similar to B. geoffrayi from Cambodia in leaf shape (narrowly ovate with an attenuate apex), except that B. geoffrayi has much larger leaves (up to 18.5 × 10 cm) and the capsule wings are pointed and the longest is up to 11 mm long, compared with the rounded ones of B. phamiana , where the longest wing is c. 7 mm long.

According to label data, this species flowers and fruits in June, July and August.

DISTRIBUTION

Cambodia (Île du Pic) and South Vietnam (Bà Ria-Vung Tâu [Île de Côn Dao]).

HABITAT

Locally common, in shaded, humid conditions below the tree canopy, on soil with humus, close to the river bed.