The name comes from gymnos, meaning naked and calyx is the collective term for sepals and is therefore naked flower buds with no hair nor spines. From an early age, these have flowers and they can last for a number of days. Within the genera, there are many plants with some being solitary, others not and some stems. The natural habitat is in South America with many up the mountains.
Gymnocalycium mihanovichii hibotan is a grafted cacti and its common names are either Ruby ball or Japan. The colour is formed with it being bred without chlorophyll and put on a rootstock, which supplies its requirement, e.g. food. Mine is red in colour, however they can be obtained in other colours. In case you wonder, without the rootstock this would die, yet Gymnocalycium mihanovichii, which is a natural colour, does survive.
This is again my lack of knowledge, but I am sure it is within the Gymnocalycium family, yet no idea of its species.
Adromischus ~ Astrophytum ~ Cephalocereus ~ Cereus ~ Cyanotis ~ Echinopsis ~ Epiphyllum ~ Espostoa ~ Ferocactus ~ Frithia ~ Haworthia ~ Hildewintera ~ Lithops ~ Lophocereus ~ Mammillaria ~ Notocactus ~ Opuntia ~ Pilosocereus ~ Rebutia ~ Schlumbergera ~ Sedum ~ Sempervivum ~ Stenocereus ~ Sulcorebutia ~ Tephrocactus ~ Turbinicarpus ~ Weberbauerocereus