Pollination

Pollination is the transfer of pollen from an anther to a stigma. Fertilisation is what happens afterwards: the pollen grain grows a pollen tube down through the style to an ovule, and the male nucleus travels down it and joins with the nucleus of the egg cell. They are not the same thing.

	Insect-pollinated flowers	Wind-pollinated flowers
Petals	Large, brightly coloured, often scented	Small, dull or green, or none
Nectar	Yes, as a reward	None
Anthers	Inside the flower, where an insect brushes past	Hanging outside on long filaments, in the wind
Pollen	Sticky or spiky, so it clings to insects; smaller amounts	Light and smooth, so it floats; huge amounts, because most is lost
Stigma	Sticky, inside the flower	Feathery, hanging outside to catch pollen from the air
Examples	Buttercup, foxglove, apple, rose	Grasses, hazel, oak, birch

From pollination to seed: pollen lands on a stigma → a pollen tube grows down the style → the male nucleus joins the egg cell in an ovule (fertilisation) → each fertilised ovule becomes a seed → the ovary swells into a fruit round the seeds. An apple is a swollen ovary; the pips are seeds. A pea pod is a fruit; the peas are seeds.

Stretch Pollen carried to a different plant of the same kind is cross-pollination; the offspring get a new mix of genes, which gives variation. Pollen landing on the same plant is self-pollination. Some flowers are pollinated by birds, bats or beetles rather than bees; moth-pollinated flowers are often pale and scented at night. Darwin predicted a moth with a tongue 30 cm long from the shape of an orchid, and it was found forty years later.