Photo by Dirk Bellstedt
Growing in nature in Bulolo Gorge, South Africa
S. primulifolius, closely related to the similar S. rexii (which is an ancestor of most modern hybrids), sometimes grows epiphytically and lithophytically. It is quite variable, as can be seen from other photos here and here, and there is also a white form. At one time, S. formosus was considered a subspecies, S. primulifolius ssp. formosus.