Survey of <i>Lagerstroemia</i> L. (Lythraceae) in Indochina (excl. Thailand) with the description of <i>Lagerstroemia densiflora</i>, sp. nov., a new species from Vietnam

Lagerstroemia L. (Lythraceae) in Indochina (Cambodia, Laos, and Vietnam) comprises 21 species. Six species, namely Lagerstroemia densiflora W.J.de Wilde & Duyfjes, sp. nov., L. gagnepainii Furtado & Srisuko, L. kratiensis W.J. de Wilde & Duyfjes, L. micrantha Merr., L. lecomtei Gagnep., L. petiolaris Pierre ex Laness., only occur in Indochine. Lagerstroemia densiflora W.J.de Wilde & Duyfjes, sp. nov., from Vietnam, is new to science; it differs from the most similar Lagerstroemia duperreana Pierre ex Gagnep. by a compact and densely flowered inflorescence, the calyx tube smooth and unridged, the pseudopedicel at anthesis 3-4 mm long, in fruit 4-5 mm long, and the glabrous capsules with a smooth surface. For each species the original reference, typification, spot- characters and distribution are presented. There are two keys to the species, one for flowering and one for fruiting material.