Two new species of Begonia L. (Begoniaceae) from central Laos

(expectedly sect. Platycentrum ) is endemic of Vientiane province (Vang Vieng district). In morphology of staminate flowers, it allies to B. subhowii described from southeastern Yunnan. From B. subhowii and related B. howii , new species differs in larger leaves, entire leaf margin, leaf petiole quadrate in cross section and very small, caducous inflorescence bracts. Leaf petiole quadrate in cross section, is unique character in the genus. The second species, B. tatianae (sect. Diploclinium ) named after its discoverer and grower – Mrs. Tatiana Maisak, allies to B. cladotricha , B. gesneriifolia and B. hinnamnoensis originated from limestone formations associated with Hin Nam No Nature Protected Area (central Laos and Vietnam). From allied species, our plant differs in miniature habit, glabrous leaves above dark green, with large diffuse white spot (with small white crystalloid bodies), few stamens, pistillate flowers normally having 4 tepals and ovary bearing wings of distinctly unequal size. Both described species represent characteristic native element of aboriginal limestone flora of lowland karstic formations in central part of Laos.


Begonia quadripetiolata
Etymology. The species epithet refers leaf petioles quadrate on cross section.
Ecology, phenology and conservation status. Primary and secondary, seasonally dry, broadleaved, evergreen forests on solid highly eroded rocky crystalline limestone at elevations 550-650 m a. s. l. Lithophytic herb growing in crevices of vertical shady cliffs in middle part of hill slopes. Flowers in culture April-May. Locally very common. Estimated IUCN Red List status -LC.
Distribution. Limestone areas of central Laos, Vientiane province (Vang Vieng district). Local endemic, only known from type locality.

Begonia tatianae
Ecology, phenology and conservation status. Primary, seasonally dry, broad-leaved, evergreen and semideciduous forests on solid highly eroded rocky crystalline limestone at elevations 350-450 m a. s. l. Lithophytic herb growing in crevices of vertical shady cliffs on tops and in upper part of hill slopes. Flowers in culture April-May. Not common, usually forms very small populations. Estimated IUCN Red List status -DD.
Distribution. Limestone areas of central Laos, Khammouane province (Boualapha district, northeastern part of Hin Nam No Nature Protected Area). Local endemic, only know from type locality.
Notes. New species morphologically allies to Begonia cladotricha M. Hughes, B. gesneriifolia Aver. and B. hinnamnoensis Souvann. et Lanors. originated from limestone karstic area associated with limestone formations of Hin Nam No Nature Protected Area and Quang Binh province (central Vietnam). All mentioned species belong to Begonia sect. Diploclinium sharing such diagnostic characters as a short, tuberous rhizome, stemless habit, axillary inflorescences, reniform leaves, threelocular axillary bilamellate placenta and dry winged fruit. From allied species our plant clearly differs in miniature habit with inflorescence 10-16 (vs. inflorescence 25-30 cm long), leaves above dark green, with large diffuse white spot, glabrous, finely papillulose, with small white crystalloid bodies (vs. leaves above pale gray-green, brown or green mottled with purple, more or less bullate, hairy at least below, without white crystalloid bodies), all parts of plant glabrous, except ovary, hairs when present stellate with three branches (vs. almost all plant hairy with scurfy or erect hairs, branched at base with 3-4 branches), number of stamens 6-12 (vs. number of stamens about 19), pistillate flowers normally with 4 tepals (vs. pistillate flowers normally with 5 tepals), 2 ovary wings large subequal, 1 wing distinctly smaller (vs. all ovary wings subequal). All four species are local endemics forming characteristic native element of aboriginal limestone flora of lowland karstic formations in central part of Laos and Vietnam.