Greek kleistos—closed, referring to the unexpanded flower.
Body mostly shrubby, erect, prostrate or pendulous, narrowly cylindric. Ribs 5-30, low. Areoles with and without flowers mostly the same. Flowers narrow, tubular, red, orange, yellow or green; stamens in 2 groups, the lower one on a rim over the nectar chamber. Flower tube straight, bent or s-shaped and, together with the pericarpel, covered with scales that are woolly or hairy in the axils. Fruit small, spherical, fleshy, sometimes with hairs and usually with perianth remnants persistent. [Borzicactus Riccob.]
Narrow tubular 'closed' flowers (adapted to pollination from humming-birds) with stamens in 2 groups; fruit spherical, 1-4 cm wide.
40-50 species from C Peru to Bolivia, N Argentina, Paraguay, Uruguay.
Source: (1997). Cactaceae. In: . Horticultural Flora of South-eastern Australia. Volume 2. Flowering plants. Dicotyledons. Part 1. The identification of garden and cultivated plants. University of New South Wales Press.