Senna Mill.
Herbs, shrubs or trees, not armed. Lvs paripinnate or reduced to phyllodes; petiolar glands often present; stipules various. Infl. axillary, racemose or paniculate; bracts and bracteoles various. Calyx with a very short tube and 5, often unequal, segments imbricate in bud. Corolla usually yellow, rarely white; petals subequal. Stamens free, 10 and all fertile, or some reduced to staminodes, or 5 and fertile; anthers uniform or a few larger, basifixed, opening by the apex. Style curved; stigma terminal. Pod various, compressed or terete, 1-2-valved, or indehiscent.
Key
c. 240 spp., tropical and subtropical, especially America. Naturalised spp. 3.
The 3 Senna spp. naturalised in N.Z. are usually placed in Cassia sens. lat. However, the 3 subgenera traditionally accepted for Cassia are so distinct that their elevation to generic rank is now recommended by Irwin, H. S. and Barneby, R. C., in Polhill, R. M. and Raven, P. H. (Eds), Advances in Legume Systematics 1: 97-106 (1981), and Mem. New York Bot. Gard. 35: 1-918 (1982).
