Trees, unarmed. Stems spreading, glabrous or silky-hairy when young. Leaves alternate, even-pinnate; stipules present, caducous; petiolate; extrafloral nectaries absent; leaflets 6–16[–50], blade margins entire, surfaces glabrous or slightly hairy. Inflorescences 20+-flowered, usually terminal, racemes; bracts present, caducous [persistent]; bracteoles present. Flowers caesalpinioid, hypanthium solid; calyx usually caducous, rarely persistent, zygomorphic, turbinate or vase-shaped, lobes 5; corolla yellow [pink, red, or white], blades narrowed to claw; stamens 10, heterantherous, usually 3 staminodes, 4 shorter stamens, length of 3 longer stamens to 2 times shorter; filaments glabrous, nearly same length as anthers, staminodes and short stamens linear, long stamens sigmoidal; anthers dorsifixed, dehiscing by lateral slits and/or basal pores; style terminating in minute stigmatic cavity. Fruits legumes, stipitate, usually linear in profile or cylindrical, sometimes rectangular-cuboid, indehiscent, woody, glabrous. Seeds 40–100, obovoid-ellipsoid. x = 12, 14.

Distribution

Introduced; Florida, nearly worldwide in tropical areas.

Discussion

Species ca. 32 (1 in the flora).

Cassia in the broad sense first became known to European botanists through the fruits that were used in herbal medicines imported from Asia by way of Egypt and Asia Minor (L. T. F. Colladon 1816; H. S. Irwin and R. C. Barneby 1982). Only three species were known to J. P. de Tournefort (1700) when he first defined the genus. Characterized by a long taxonomic history, Cassia was considered to be the twentieth largest flowering plant genus (D. G. Frodin 2004), including approximately 600 species (Irwin and B. L. Turner 1960), before being subdivided into the smaller Cassia in the strict sense, and the almost equally large Chamaecrista and Senna (Irwin and Barneby 1981, 1982). This division has been supported by morphological (S. C. Tucker 1996; T. Boonkerd et al. 2005) and molecular phylogenetic (A. Bruneau et al. 2008) studies. In the latter, Cassia and Senna are sister genera; Chamaecrista appears more distantly related. In contrast to Chamaecrista (A. Conceição et al. 2009) and Senna (B. Marazzi et al. 2006), phylogenetic relationships within Cassia are still unclear.

Flowers of Cassia are pollinated by bees, which vibrate the flowers to release pollen from the anthers (G. Gottsberger and I. Silberbauer-Gottsberger 1988).

Cassia trees are appreciated as ornamentals in gardens and parks and along streets throughout the tropics and subtropics, owing to their showy yellow [or pink] flowers. In North America, trees are cultivated especially in California and Florida, and escaped specimens of the most widely cultivated species, C. fistula, have become naturalized occasionally in Florida (R. P. Wunderlin and B. F. Hansen, www.florida.plantatlas.usf.edu). Other commonly cultivated species are C. grandis Linnaeus f. (coral shower tree; from Central America and South America) and C. javanica Linnaeus (pink shower tree, apple blossom cassia, Java cassia; from southeast Asia). Cassia leptophylla Vogel (gold medallion tree; from Brazil) is often cultivated in southern California, and C. roxburghii de Candolle (red or Ceylon cassia; from India and Sri Lanka) is cultivated in Florida. The presence of a sixth cultivated species, C. afrofistula Brenan (Kenyan shower tree; from Africa and Madagascar), in Florida needs confirmation.

Selected References

None.

Lower Taxa

Cassia fistula