The flowers or inflorescence of this family actually consist of a packed cluster of individual flowers known as capitulum. There are 2 types of flowers in a capitulum. The ones on the outside which resemble petals are called ray flowers (ligulate) while those inside are called disk flowers (tubular). Not all capitula have ray flowers. Those without ray flowers are called discoid capitula. Another family name of this group of plants is Compositae, which is derived from the composite nature of the flowers.
Online reference: | Ohio Plants |