A pollinium (: pollinia) is a coherent mass of

pollen Pollen is a powdery substance produced by most types of flowers of seed plants for the purpose of sexual reproduction. It consists of pollen grains (highly reduced Gametophyte#Heterospory, microgametophytes), which produce male gametes (sperm ...

grains in a plant that are the product of only one

anther The stamen (: stamina or stamens) is a part consisting of the male reproductive organs of a flower. Collectively, the stamens form the androecium., p. 10 Morphology and terminology A stamen typically consists of a stalk called the filament ...

, but are transferred, during pollination, as a single unit. This is regularly seen in plants such as

orchid Orchids are plants that belong to the family Orchidaceae (), a diverse and widespread group of flowering plants with blooms that are often colourful and fragrant. Orchids are cosmopolitan plants that are found in almost every habitat on Eart ...

s and many species of milkweeds (

Asclepiadoideae The Asclepiadoideae are a subfamily of plants in the family Apocynaceae. Formerly, it was treated as a separate family under the name Asclepiadaceae, e.g. by APG II, and known as the milkweed family. They form a group of perennial herbs, twinin ...

). 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. Most orchids have waxy pollinia. These are connected to one or two elongate stipes, which in turn are attached to a sticky viscidium, a disc-shaped structure that sticks to a visiting insect. Some orchid genera have mealy pollinia. These are tapering into a caudicle (stalk), attached to the viscidium. They extend into the middle section of the

column A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member ...

. The pollinarium is a collective term that means either (1) the complete set of pollinia from all the anthers of a flower, as in Asclepiadoideae, (2) in Asclepiadoideae, a pair of pollinia and the parts that connect them (corpusculum and translator arms), or (3) in orchids, a pair of pollinia with two viscidia and the other connecting parts. Milkweed pollinia are housed within a stigma chamber at the bottom of

slits of its flower. A

pollinating Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds. Pollinating agents can be animals such as insects, for example bees, beetles or butterflies; birds ...

insect often stumbles in such a way that its legs fall down the slits, then pull up the pollinia as it tries to free its legs; the pollinia can be carried to another flower and dropped down the latter's slits to achieve pollination. However, the insect sometimes fails to retract its legs from the slits and is trapped there until it dies. File:Pollinia Phalaenopsis (1).jpg, The waxy pollinia of a ''Phalaenopsis'' File:Phaleanopsis pollinia.jpg, Pollinia of a ''

Phalaenopsis ''Phalaenopsis'' (), also known as moth orchids, is a genus of about seventy species of plants in the family Orchidaceae. Orchids in this genus are monopodial epiphytes or lithophytes with long, coarse roots, short, leafy stems and long-lastin ...

'' orchid File:Ophrys apifera flower2-der.jpg, Pollinium of ''

Ophrys apifera ''Ophrys apifera'', known in Europe as the bee orchid, is a perennial plant, perennial herbaceous plant of the genus ''Ophrys'', in the family of Orchidaceae. It serves as an example of Sexual mimicry#Interspecific deceptive mimicry, sexually d ...

'' File:Asclepias syriaca-pollinia.jpg, Pollinia of ''

Asclepias syriaca ''Asclepias syriaca'', commonly called common milkweed, butterfly flower, silkweed, silky swallow-wort, and Virginia silkweed, is a species of flowering plant. It is native to southern Canada and much of the United States east of the Rocky Moun ...

'' 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 ''Asclepias asperula'', commonly called antelope horns milkweed or spider milkweed, is a species of milkweed native to the Southwestern United States and northern Mexico. Description It is a perennial plant growing to 0.3–0.9 m (1–3 ft ...

'') with pollinia attached to legs File:Xylocopa virginica pollinia closeup.jpg, Pollinia of milkweed (''Asclepias'') on the legs of carpenteer bee (''

Xylocopa virginica ''Xylocopa virginica'', sometimes referred to as the eastern carpenter bee, extends through the eastern United States and into Canada. They are sympatric with ''Xylocopa micans'' in much of southeastern United States. They nest in various types of ...

'') File:Dolichovespula maculata-pollinia.jpg, Pollinia of milkweed (''Asclepias'') on the legs of bald-faced hornet (''

Dolichovespula maculata ''Dolichovespula maculata'' is a species of wasp in the genus '' Dolichovespula'' and a member of the eusocial, cosmopolitan family Vespidae. It is taxonomically an aerial yellowjacket but is known by many colloquial names, primarily bald-faced ...

'') File:Apis mellifera-pollinia.webm,

Honeybee A honey bee (also spelled honeybee) is a eusocial flying insect within the genus ''Apis'' of the bee clade, all native to mainland Afro-Eurasia. After bees spread naturally throughout Africa and Eurasia, humans became responsible for the c ...

with a leg trapped in

common milkweed ''Asclepias syriaca'', commonly called common milkweed, butterfly flower, silkweed, silky swallow-wort, and Virginia silkweed, is a species of flowering plant. It is native to southern Canada and much of the United States east of the Rocky Moun ...

pollinia slits

References

{{Commons, Pollinium (Orchidaceae) Pollination Plant anatomy Orchid morphology