There are about 33 species of Acmadenia, belonging to the Rutaceae family comprising some well-known plants including citrus, buchu and rue.
The leaves and fruit of these plants bear tiny oil glands that imbue each species with its own characteristic scent. (Think of the Citrus genus.) The aromas are strongest when the leaves are crushed.
Most of the acmadenias are endemic to fynbos in the south-western Cape, while some grow as far east as the old Ciskei of the Eastern Cape.
There is an Australian genus of Rutaceae called Boronia that bears fragrant flowers and is used commercially for producing oils (Wikipedia).
The plant in picture, Acmadenia mundiana, has become a rewarding gardening subject, an ornamental shrub for rockeries and pruned borders. In spite of its natural limestone habitat the plant performs well in average garden soil and circumstances, even as a container plant (www.plantzafrica.com).