Woody vines, occasionally described as shrubs or small trees; stipules very small, borne on petiole at or slightly above base or on stem beside base of petiole, occasionally absent; leaves opposite; petiole occasionally eglandular but usually bearing 2 glands between middle and apex, the glands lateral to somewhat adaxial; lamina eglandular or rarely biglandular on margin at very base. Inflorescences axillary and terminal, paniculate with the branches sometimes subtended by much-reduced leaves, open and many-flowered, the flowers ultimately borne in pseudoracemes; bracteoles eglandular; pedicels sessile, straight in bud. Sepals all eglandular; corolla radially symmetrical or nearly so, the petals subequal in size and shape but 1 with the claw wider than the other 4; petals white, glabrous or sericeous abaxially, spreading to (usually) strongly reflexed during anthesis; filaments glabrous, very slender, straight, erect and exserted, longer opposite sepals than opposite petals or subequal; anthers mostly glabrous but rarely abaxially sparsely sericeous, with the connective flat and narrowly linear, hardly or not at all swollen abaxially; ovary with carpels connate their whole length; styles alike or 1 shorter than the other 2, of uniform diameter, the stigma terminal or slightly internal, truncate or slightly capitate. Samaras separating from a pyramidal torus; samara butterfly-shaped with the lateral wings chartaceous, cleft to nut at apex and base; dorsal wing small to absent; intermediate outgrowths absent or present. Chromosome number unknown.
This genus is very distinctive because of its nearly radial white corollas and eglandular sepals. There is nothing like it in Mexico or Central America; indeed, there is hardly anything like it anywhere in the New World. To find other genera with eglandular sepals and radial white corollas one needs to look to Madagascar, where Madagasikaria C. Davis, Rhynchophora Arènes, and Sphedamnocarpus Hook. f. are similar in their flowers (but not in their fruits). The samaras of Psychopterys resemble those of Hiraea and its close sisters; otherwise, there is very little in the morphology of these plants to suggest that they would find a home in this clade. See the discussion in the revision cited below.