Flower:  modified Shoot
Floral appendages:  modified leaves

Four 'whorls' of appendages

non-reproductive (perianth) positioned
beneath reproductive

Gynoecium at the top, calyx at the base

Gynoecium can be represented by many, separate carpels (apocarpous), a single structure made up of more than 
one carpel (syncarpous-compound pistil), or a single carpel (simple pistil)
 

Calyx+Corolla+Androecium = androperianth