Dahlia flower. Close-up of the flower" of a dahlia (Dahlia sp. ), a popular garden plant and member of the Compositae family. This "flower" is actually a cluster of small individual flowers, or florets, with the outer florets maturing first. The broken colour in flowers like these can be caused by genetic mutations induced by "jumping genes" (transposons) that move around in the plant's DNA. Dahlias originate from a handful of Mexican species that have been continuously inter- bred and hybridised to produce new forms since their introduction to Europe in 1789. Over 20 species are recognized today."