callistephus

from The Century Dictionary.

• noun A genus of composite plants, containing a single species, C. Chinensis, the China aster, which has been long in cultivation, and is much prized as a hardy annual, remaining long in flower.

from the GNU version of the Collaborative International Dictionary of English.

• noun a genus of plants having only one species, an erect Asiatic herb with large flowers.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun one species: erect Asiatic herb with large flowers