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 core pollen grains and stratigraphy of the core so researchers frequently select locations where the sediments are under anaerobic conditions. The cores are then subjected to pollen analysis by palynologists who are able to infer the proportions of major plant types from the concentrations of different pollen types found in the cores. There are a number of tools used for coring, often with specialized uses: Pollen core A pollen core is a core sample of a medium containing a stratigraphic sequence of pollen. Analysis of the type and frequency of the pollen in each layer is used to study changes in