Solitary axillary flowers, pedicles 8-20 (-26) mm in length, basally bibracteolate; 5-lobed calyx, with unequal lobes, more or less free to the base, imbricate, the adaxial lobe widely lanceate to ovate, 5–9.5 mm long and 3–6 mm wide, slightly accrescent, the 2 middle lobes longer and overlapping, the 2 abaxial lobes nearly the same size as the adaxial and overlapping the middle lobes; 5-lobed corolla, 7–8 mm long, yellow with purple at the throat, bearded at the mouth; 4 fertile stamens.

[12] The genus was described by Ruiz & Pav., published in Florae Peruvianae, et Chilensis Prodromus 95.

The genus is named after Antonio Meca y Cardona, who founded the botanical gardens in Barcelona, in 1784.

[14][15] [16] Rossow (1987) in his taxonomic revision of the genus, recognized ten species.

Sold as an ornamental garden flower, such as Mecardonia Magic Carpet Yellow, as annuals in colder areas.