This plant grows wild in arid habitats, and has spherical leaves to reduce its surface area and help to conserve moisture. (Well... they should be spherical, but apparently I've not been giving mine enough water.) The centre of the leaf contains special transparent cells for storing water. However, this leaf shape is a disadvantage when it comes to photosynthesis, so it has made yet another rather curious adaption. Each leaf has a narrow band of transparent tissue, and this lets light in like a window. The leaf is then able to photosynthesize from the inside as well as from the outside.
Cross section through a leaf:
Soon after it arrived, our plant also produced a rather bizarre flower. Although belonging to the daisy family, this flower has only disc florets and no ray florets and looks more like a little brush than a daisy.