Crassula subaphylla var. subaphylla old flowers

The earlier, cream petals of the small Crassula subaphylla var. subaphylla flowers grown in flat-topped inflorescences turn brown rather quickly, while the shorter sepals remain green for longer.

The protective covering provided by calyces at budding time is more durable than the colourful flourish of corollas during the short-seasoned pollination visitations. This is because calyces in many flowering plants including the Crassula genus, still serve ovaries when the flowers are gone and fruits develop inside them.

Calyces are here considerably shorter than corollas. This is also functional, as the taller stamens with anthers and styles with stigmas become unimportant once fruiting commences and they can safely be abandoned by the plants defences (Smith, et al, 2017; iNaturalist).