(photo above: Barrel cactus fruit and black seeds, Jason)
Additional Reading: Cactus Seed Germination
Opuntia macrorhiza fruit with seeds, Tony Frates
Barrel cactus fruit with dried flower, David Leonard
Pitaya fruits, Sam Blackman
Astrophytum myriostigma seeds, Kathy
Tiny actus seedling with seed coat , Peter Baur
Echinocactus polycephalus xeranthermoides seed, USGS
Echinocactus polycephalus polycephalus seed, USGS