Androecium organization

Schonenberger, J. and Grenhagen, A. (2005). Early floral development and androecium organization in Fouquieriaceae (Ericales). Plant Systematics and Evolution, 254, 233-249. 

The Androecium or Stamen System.—The andracium is the single or double whorl of male organs situated within or above the corolla. It is composed of stamens or microsporophylls. 

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). 

---