Koyamasia

Perennial herbs. Stems erect, pubescent. Leaves simple, alternate, petiolate, lamina ovate or elliptic, margin serrate, apex acute or acuminate, base attenuate. Capitulescences terminal, solitary or paniculate. Capitula discoid, homogamous; pedunculate, florets bisexual and fertile. Involucre imbricate, phyllary tips recurved. Florets 60–100; corollas purplish or white, actinomorphic; corolla lobes 5. Anthers 5, syngenesious. Styles 2-branched, inner surface covered with stigmatic papillae, outer surface covered with sweeping hairs reaching to below style bifurcation. Achenes subterete, 10-ribbed, carpopodium absent. Pappus in one series of bristles, deciduous. Pollen echinolophate, 3-porate, without micropuncta. Three species are recognized in Thailand.