This is another illustration of the propensity of Streptocarpus species for growth in rocky locations. Under these conditions, the roots will be lodged in the very narrow confines of clefts in the rock, or shallowly within moss. During wetter seasons, the plants will be well-drained but always moist — during drier months the plant adapts by substantially reducing the amount of its living leaf surface (through which moisture transpires). The dead outer portions of the leaf die and dry up.
Note the white ribs on this attractively-foliaged species. A closeup of the flowers can be seen by clicking here. A mauve form of prolixus, planted several to a common pot, shows the variable nature of the species. Other photos of a cultivated plant, somewhat different in flower form, can be seen here.