Frailea
Frailea is a genus of globular to short cylindrical cacti native to South America.
Description
They are characterized by low-growing, flattened-spherical to short-cylindrical stems that often form multiple shoots, though sometimes grow solitary. These stems have weakly developed ribs and tubercles, adorned with small spines. The short, funnel-shaped flowers emerge from the tip of the shoot. They are notable for their limited opening, often blooming only briefly during the day. A significant characteristic of most Frailea species are cleistogamous, where flowers self-pollinate and produce seeds without ever opening. This occurs because the anthers develop in contact with the stigma, allowing for self-fertilization within the closed bud. Cleistogamy is believed to be an adaptation to protect against adverse weather conditions that could impede pollination, especially during their summer flowering period which coincides with significant rainfall. The areoles on the pericarpel and flower tube are densely covered with woolly hairs and bristles.The fruits are thin-walled, dry, and packed tightly with seeds. They may retain a persistent floral remnant and can open irregularly or remain indehiscent. The seeds, measuring up to 1.5 millimeters in length, are broadly ovate or cap-shaped.