Bananas do have seeds, they normally fail to mature and can be seen as the small dark soft specks towards the centre of the fruit. It seem to remember that only 1 fruit in 100,000 will be fertilised and the seeds reach maturity.
There are species of wild bananas that have big
seeds. But people prefer eating those with minute seeds. So in the cultivated varieties the seeds exist only in the form of very small black dots or specks. So these
bananas only we see in the markets.
The big seed varieties of bananas with big seeds exist and they are found in markets of Indonesia, it seems.
