Cape Iris

 Dietes iridioides

Evergreen perennial herb to 60 cm high, with a creeping rhizome. Leaves sword-shaped, in a loose fan, dark green. Flowers subtended by sheating bracts, each lasting a single morning, white with the inner petals often marked with brown streaks near the base and the style branches lightly flushed with violet, 30 - 40 mm diameter.
Quotation: John Manning: Wildflowers of South Africa, Pretoria, 2003
These photos are from Uni Bochum.