This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
Dwarf herbs, rarely frutescent. Petals 5, free, or connate at the base only. Stamens and carpels of the same number. Leaves sessile, opposite, usually more or less fleshy, entire, glabrous, or ciliate. Nearly all of the species, numbering 150, are from South Africa, a few from the Himalayas. There are* no hardy species in cultivation, but some of them are employed for bedding out in Summer. The name is the diminutive of crassus, thick or fleshy.
1. C. coccinea (fig. 101), syn. Kalosanthes coccinea. - This is the only species in general cultivation. It grows about 2 feet high, and produces large clusters of crimson, scarlet, rose or pink flowers, according to the varieties.
Fig. 101. Crassula coccinea. (1/3 nat. sice.)