At least one viable pollen grain must be deposited on the stigma and fertilize an ovule if a seed is formed.
(At least one viable pollen grain; must be deposited; on the stigma) (At least one viable pollen grain; fertilize; an ovule) (a seed; is formed; )
At least one viable pollen grain At least one viable pollen grain a seed
must be deposited fertilize is formed
on the stigma
an ovule