Out of several hundred species of Cassia known (and they occur in all the warmer parts of the globe except Europe), only two are grown outside in Britain, and of these the first species is decidedly tender, while the second, though hardy, scarcely qualifies as a woody plant. Cassia belongs to the sub-family Caesalpinioideae, in which the petals are equal, or almost so, in size and shape. Stamens usually ten, but three or five of these may be absent, or reduced to staminodes. Leaves pinnate, with an even number of leaflets. The fruits of certain Near Eastern species are the senna pods of druggists; those of the beautiful Indian laburnum (C. fistula) attain a length of 2 or even 3 ft.