The genus Adromischus is part of the Crassulaceae (stonecrop or orpine family) found growing with other leaf succulents in dry areas all over southern Africa. Adromischus is closely related to other southern Africa Crassulaceae: Tylecodon, Cotyledon—and it's not far from Kalanchoe. Adromischus (known as "adros" by afficionados) are found in every province of S Africa and in southern Namibia. Like this plant, they are all subshrubs or smaller. Luckily they do not seem to be in serious danger of extinction, though habitat loss can always threaten to wipe out specific forms occurring in tiny areas.
This species A marianiae forma herrei and its close relatives are found in westerly parts of Western Cape and Northern Cape.
I raised this plant from a tiny individual of 3 small leaves to the 14-leaf specimen you see here. It's still just over 3 inches from tip to tip. Although it has won a couple awards, I can't claim any great skill with this drop-dead gorgeous plant. I do watch it carefully, but I'm guessing that my Los Angeles climate and my rather negligent hand with the watering bucket just happen to favor it.
Adromischus marianiae is a large and complex species with many different subspecies or forms stretching hundreds of miles north-south in western South Africa. The size, shape and color of the succulent leaves varies widely, even within the "herrei" form. Some have leaves of a pale bluish green with maroon spots, others have red leaves, still others are nearly black. They grow rather slowly; they are small; some of them are rather difficult to grow well unless the climate is just right. Many of these forms are highly desirable and sometimes difficult to find.
See AlsoPilbeam, J.; Rodgerson, C.; Tribble, D. 1998. Adromischus. Cirio Publishing Services Ltd. Southampton. ISBN: 0 9520382 4 8.
Adromischus marianiae forma herrei at Adromischus Displayed, by Derek Tribble