Composite family

The sunflower family (Asteraceae or Compositae) is a family of dicot flowering plants.

Asteraceae is a large and diverse family whose typical inflorescence (what many people mistake for a single flower) is a densely packed cluster of many individual flowers called florets. The arrangement of florets within this cluster (or head) is such that each flower is separated from the next by approximately the golden ratio, producing a pattern of spirals where the number of left spirals and the number of right spirals are successive Fibonacci numbers.

Members of the Asteraceae have one or both of two kinds of florets. The outer-most perimeter of composites like the sunflower is composed of a row of florets each possessing a long strap-like petal, termed ligule; these are the ray flowers. The inner portion of the flower (or disc) is composed of small flowers with tubular corollas[?]; these are the disc flowers. The composition of Asteraceous inflorescences varies from all ray flowers (like dandelions, genus Taraxacum) to all disc flowers (like pineapple weeds[?]).

The composite nature of these inflorescences led early taxonomists to call this family the Compositae. Since most plant families have the suffix -aceae, efforts to make the family name more standard motivated changing the name from Compositae to Asteraceae.

References ITIS report 2002-09-10 (http://www.itis.usda.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=35420)

Dirk R. Walters and David J. Keil (1996). Vascular plant taxonomy. 4th ed. Kendall/Hunt Publishing Company. Dubuque, Iowa