Pollination rigida", this allows the plant to self-pollinate, which is useful when biotic pollinators in the environment have decreased. It is possible for a plant have varying pollination methods, including both biotic and abiotic pollination. The orchid "Oeceoclades maculata" uses both rain and butterflies, depending on its environmental conditions. More commonly, pollination involves pollinators (also called pollen vectors): organisms that carry or move the pollen grains from the anther of one flower to the receptive part of the carpel or pistil (stigma) of another. Between 100,000 and 200,000 species of animal act as pollinators of the world's 250,000 species of flowering
Pollen tube grains are deposited in the micropyle of the ovule of a female cone or megastrobilus, where they mature for up to a year. In conifers and Gnetophytes the pollen germinate to produce a pollen tube that penetrates the megasporangium or nucellus carrying with it sperm nuclei that are transferred to the egg cell in the developing archegonia of the female plant. The female sporophyte must recognize the pollen stuck to the stigma. Often, only pollen of the same species can successfully grow and outcrossed pollen is more successful in growing. With self-incompatibility systems, outcrossed pollen grows and outcompetes self pollen.