In the given figure of flower, the structure marked as
A, B, C and D are respectively gynoecium, stamen, ovule
and thalamus.
Gynoecium constitutes the inner essential whorl flower
comprising carpels. Carpel is the unit of gynoecium. Each
carpel contains ovary and stigma. Ovules are produced
within ovary. Stamen is the male fertilizing organ of a flower,
typically consisting of a pollen-containing anther and a
filament. Ovule is the part of the ovary of seed plants that
contains the female germ cell and after fertilization becomes
the seed. Thalamus is an expanded tip of the pedicel.
Components of whorls are concentrically arranged on a
thalamus.
