Deux nouvelles espèces d’euphorbes (Euphorbia L. section Goniostema, Euphorbiaceae) de la région de Fort-Dauphin, Madagascar

摘要

Two new spurges (Euphorbia L. sect. Goniostema Baill. ex Boiss., Euphorbiaceae), from the surroundings of Amboasary Atm, Anosy region (Taolanaro), Madagascar, are described here. The first one, Euphorbia gigantea J.-P. Castillon, sp. nov., is close to Euphorbia croizatii Leandri, but differs by its general habit and especially its much larger size (up to 6 m). The second, Euphorbia valeryae J.-P. Castillon, sp. nov., whose affinities are not clear, is easily recognizable by its piliform stipules, present only on the very last cm of each stem, and by its incyathescences bearing an always single white-green cyathium.