A false fruit (accessory fruit) is one where parts other than the ovary, such as the thalamus, contribute to the fruit. Apple and strawberry are classic examples.
During
double fertilization, the fusion of one sperm with the egg cell forms the
embryo and that of the other sperm with a polar nucleus gives rise to the
endosperm. The families that lack an endosperm include Orchidaceae,
Podostemaceae, and Trapaceae.
If a fruit is formed from any other part of the flower than the ovary, then such a fruit is termed as false fruit. In apple the thallamus of the flower forms the edible part or the fruit.