The Southern region of the New Hebrides consists of five islands of very different size, clearly separated from and with a cooler climate than the remainder of the archipelago. Only the three largest islands have been studied botanically. These islands are Aneityum and Erromanga, now sparsely populated, where there is still extensive climax vegetation on the deep, infertile soils, and Tanna, with a dense human population, where, except in mountainous regions, there is scarcely anything but secondary vegetation, on generally fertile soils that are periodically rejuvenated by ash showers from a continuously active volcano. The principal vegetation types recognized are: dense Agathis (kauri) - Calophyllum forest; cloud forest, with mosses and ferns, on ridges above 500 m altitude; low forests or thickets with Euphorbiaceae, Hibiscus or Leucaena; open Acacia spirorbis forest; thickets of Myrtaceae and Vaccinium; various associations more or less dominated by grasses. The flora, though relatively rich in the New Hebridean context, appears poor in comparison with that of Fiji, to which it is nevertheless fairly closely related, and even poorer in comparison with that of New Caledonia. Its wider affinities are Malaysian.