This section is from the book "Handbook Of Hardy Trees, Shrubs, And Herbaceous Plants", by W. Botting Hemsley. Also available from Amazon: Handbook of hardy trees, shrubs, and herbaceous plants.
A small group of annuals of close affinity with Coreopsis; but the achenes are long and narrow, and covered with minute tubercles, and closely embraced by the bracteoles of the receptacle, which fall away with them. The pappus consists of two short stout bristles. Natives of North America.
1. C. Burridgeanum. - About 18 inches high. Leaves finely cut. Capitules on long naked slender peduncles, about
2 inches in diameter. Ray-florets about eight. In the original variety the disk is purple, and the ray bright orange with a purple spot at the base of each floret; but under cultivation it has varied. One of the prettiest variations, called atropurpureum, has the heads of a crimson-purple bordered with orange.
C. filifolium has the rays entirely yellow with a brown disk; and C. Eng-elmannii is a dwarf species with wholly yellow flowers.