ray flower

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of the small tubular flowers having a corolla with a long strap-shaped lobe, found in the flower heads of certain composite plants, as the units of a flower head of a dandelion or the marginal units of a flower head of a daisy.

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

• noun small flower with a flat strap-shaped corolla usually occupying the peripheral rings of a composite flower