Red Haired Girl Near Tree With White Flowers

Flower specialization and pollination
Flowering plants usually face selective pressure to optimize the transfer of their pollen, and this is typically reflected in the morphology of the flowers and the behaviour of the plants. Pollen may be transferred between plants via a number of 'vectors'. Some plants make use of abiotic vectors — namely wind (anemophily) or, much less commonly, water (hydrophily). Others use biotic vectors including insects (entomophily), birds (ornithophily), bats (chiropterophily) or other animals. Some plants make use of multiple vectors, but many are highly specialised.
Cleistogamous flowers are self pollinated, after which they may or may not open. Many Viola and some Salvia species are known to have these types of flowers.