Flowers often well-developed and showy, corolla with fused petals, stamens
attached to corolla tube, often with two fused carpels.
Leaves simple or less often compound or dissected.
11 orders, 49 families, 60,000 species
20,000 species are in the Asteraceae
Diagnostic characteristics: sympetalous flowers, epipetalous stamens isomerous
and alternate with the corolla-lobes or less than the corolla lobes
Chemically, iridoids are frequent, with the exception of the Asteraceae
The Asteridae is the most advanced class of dicots. They utilize specialized
pollinators and specialized means of presenting the pollen. "Rise
of the Asteridae is closely correlated with evolution of insects capable
of recognizing complex floral patterns" - A. Cronquist.