Crassothonna Genus

Crassothonna is a genus of succulent flowering plants in the daisy family (Asteraceae), order Asterales. It comprises hairless perennial herbs, shrublets, and shrubs native to Southern Africa. Stems are little- to much-branched, thin or thick and cylindrical, sometimes fleshy and bottle-shaped. Leaves are simple, succulent, green to bluish or greyish, more or less circular, egg-, or sausage-shaped, arranged alternately along the stem on a short stalk or none at all.

Flowerheads sit singly or in few- to many-headed corymbs at the stem tips, enclosed by a single row of five to eight herbaceous bracts fused at the base into a bell-shaped involucre. Some species bear only yellow disc florets, while others combine central yellow disc florets with yellow or, in one species, white ray florets around the margin. Central florets are functionally male, with a conical, unforked style tip; marginal or outer florets are functionally bisexual, set seed, and have a slightly forked style tip. The one-seeded fruits are inferior, spindle- to inversely egg-shaped, 2–5 mm long, either hairless or covered in fine or dense silvery-white hairs that form a slimy layer when wet, topped by a pappus of numerous minutely barbed white bristles. Most species carry ten pairs of chromosomes (2n=20), though C. rechingeri is hexaploid (6n=60).

The genus was described by Swedish botanist Rune Bertil Nordenstam in 2012, segregating a group of succulent, cylindrical- to globe-leaved, tuberless species that had previously been classified within the much larger genus Othonna. DNA evidence has since linked two of its species more closely to the small annual genus Gymnodiscus than to Othonna.

Crassothonna is native to Southern Africa. Conservation assessments under the Red List of South African Plants classify most species as least concern, with notable exceptions in Crassothonna clavifolia (endangered) and Crassothonna opima (critically endangered).