Perianth simple

The Annonaceae consist of trees, shrubs, or lianas with simple, alternate, entire, pin-nately veined, typically distichous leaves (Cronquist, 1993). Often, the leaves possess secretory cells. The flowers are solitary or in various sorts of mostly basically cymose inflorescences, mostly entomophilous. The flowers are perfect or rarely unisexual. The petals are commonly trimerous perianths sepals (2) 3 (4) petals commonly come in six or two series of three (Cronquist, 1993). The seeds are often arillate, X = 7, 8,9. 

That a double perianth was reduced during evolution in many groups of eudicots has long been known. However, in some clades there was also repeated evolution of a double perianth with sepals and petals from a simple perianth with only one kind of organ or a fluctuation between both traits. An example is Caryophyllales sensu lato (APG, 2009), which originally had a simple perianth and a double perianth evolved independently in several families (Brockington et al., 2009), with petals at least in part derived from the androecium (Ronse De Craene, 2008). 

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