Flower sex refers to the presence or absence of androecium and gynoecium within a flower.
1. Perfect or bisexual(monoclinous): When a flower contains both androecium and gynoecium is called perfect flower.
2. Imperfect or unisexual (diclinous): When the flower contains only one of the essential whorls is called Imperfect flower. It is of two types:
i) Staminate flowers: Flowers only with androecium alone are called staminate flowers.
ii) Pistillate flowers: Flowers with only gynoecium are called pistillate flowers.