Description from Flora of China
Erythropsis Lindley ex Schott & Endlicher; Karaka Rafinesque.
Trees or shrubs, deciduous. Leaves simple, palmately 3-5-lobed or entire. Inflorescence paniculate or rarely racemose, axillary or terminal. Flowers unisexual or polygamous, sometimes appearing before leaves. Calyx orange-red or golden, funnel-shaped or cylindrical, (4 or)5-lobed or -partite, lobes short or divided nearly to base, reflexed. Petals absent. Male flowers: stamens 10-20, in capitate cluster at apex of androgynophore; anther 2-celled, anther cells curved; undeveloped pistil present. Female flowers: ovary 5-locular, ovoid or globose, basally enclosed by undeveloped anthers; styles basally connate; stigmas as many as carpels; ovules 2 to many per locule. Follicles stipitate, endocarp membranous, dehiscent long before maturity, foliaceous. Seeds 1 to many per follicle, on inner margin of foliaceous endocarp, globose, endosperm flat or plicate; cotyledons flat, very thin.
The relationship between Firmiana and Hildegardia Schott & Endlicher is unresolved. Kostermans (Reinwardtia 4: 281-310. 1957) used a follicle character, dehiscence vs. indehiscence, to separate the two genera. Molecular data, based on limited sampling, support a division based on floral characters, especially relating to calyx morphology, but there are unpublished molecular data that suggest that Firmiana and Hildegardia may not be distinct. Firmiana is the older of the two names.
About 16 species: tropical, subtropical, and temperate Asia; seven species (five endemic) in China.