The solitary flowers of Chasmatophyllum musculinum growing at stem-tips are notably stalked. The five sepals are unequal in size, all three-angled.
There may be a hint of purple on the outside of the yellow flower corolla, the closed flower pinkish. The petals grow in more than just one whorl, some of the inside ones shorter than the rest. The many stamens converge in an erect, central, yellow cone. There are five nectary glands in the flower base.
Flowers are only open from late afternoon until early evening. Flowering happens in summer.
The Drosanthemum-like fruit capsule has five locules. The seed is pale yellow and rough with a hooked tip (Frandsen, 2017; Smith, et al, 1998; iSpot).