Young Blonde Girl Shows Off On The Red Bed With Petals Leaves

The corolla extends from the calyx outwards. Within it are housed anatomy such as the corolla tube, anthers, stamen, and stigma. The corolla tube is not separate from the corolla, but identifies the base section (some corollas form lobes at the top, which distinguishes the petals from the corolla tube).
Genetics
The genetics behind the formation of petals, in accordance with the ABC model of flower development, are that sepals, petals, stamens, and carpels are modified versions of each other. It appears that the mechanisms to form petals evolved very few times (perhaps only once), rather than evolving independently from stamens in a large number of plants.