A pollinium (: pollinia) is a coherent mass of pollen grains in a plant that are the product of only one anther, but are transferred, during pollination, as a single unit. This is regularly seen in orchids, which have a complex pollination system, and many species of milkweeds (Asclepiadoideae). Usage of the term differs: in some orchids two masses of pollen are well attached to one another, but in other orchids there are two halves (with two separate viscidia) each of which is sometimes referred to as a pollinium. which in turn are attached to a sticky viscidium, a disc-shaped structure that sticks to a visiting insect.
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File:Pollinia Phalaenopsis (1).jpg|The waxy pollinia of a Phalaenopsis
File:Phaleanopsis pollinia.jpg|Pollinia of a Phalaenopsis orchid
File:Ophrys apifera flower2-der.jpg|Pollinium of Ophrys apifera
File:Asclepias syriaca-pollinia.jpg|Pollinia of Asclepias syriaca
File:Eucera cinnamomea with pollinium 1.jpg|Male bee (Eucera cinnamomea) with pollinium attached to its head
File:Bee on Antelope Horn-April 2015.JPG|Honeybee on antelope horn (Asclepias asperula) with pollinia attached to legs
File:Xylocopa virginica pollinia closeup.jpg|Pollinia of milkweed (Asclepias) on the legs of carpenteer bee (Xylocopa virginica)
File:Dolichovespula maculata-pollinia.jpg|Pollinia of milkweed (Asclepias) on the legs of bald-faced hornet (Dolichovespula maculata)
File:Apis mellifera-pollinia.webm|Honeybee with a leg trapped in common milkweed pollinia slits
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