Its name derives from Greek and literally means "naked calyx", in reference to the calyx of the flower, which is devoid of hairs and scales. It includes a vast number of globular cacti, consisting of stems with protruding ribs and, sometimes, transverse grooves; completing the picture with robust and often curved spines, very thick and long in some species, few and thin in others. Except for rare exceptions, they do not reach remarkable dimensions, therefore they are perfect to be cultivated in pots even in small spaces, moreover they are highly appreciated for their particular flowers: very big, often bigger than the plant itself, they assume delicate tonalities, from white to pink, which make them extremely elegant and give a touch of sophistication to the surrounding environments! According to the language of flowers, these beautiful funnels symbolize delicacy, but also the ability to withstand adversity, just like this cactus, which grows and blooms with extreme ease in the most varied environmental conditions. These cacti are particularly appreciated and sought after by green collectors for many reasons: on one hand, their globular stems, for which they are commonly called "ball cacti", with their particular colors (often due to the lack of chlorophyll, which makes them fade from green to purple); on the other hand, the contrast of the stems with the showy flowers, which does not make them classify as simple spiny plants, but makes them a real must-have in decoration of the most varied environments, both indoor and outdoor!