# Rostellum

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For the synonym of a genus of molluscs, see [Tibia (gastropod)](/source/Tibia_(gastropod)).

For the muscular structure in tapeworms, see [Rostellum (helminth)](/source/Rostellum_(helminth)).

Cutaway drawing of *[Orchis mascula](/source/Orchis_mascula)* showing the rostellum projecting forward from the [column](/source/Column_(botany)) to form cups which keep the [adhesive balls](/source/Viscidium) sticky.

The **rostellum** is a projecting part of the [column](/source/Column_(botany)) in [Orchidaceae](/source/Orchidaceae) flowers, and separates the male androecium from the female [gynoecium](/source/Gynoecium), commonly preventing self-fertilisation.[1] In many orchids, such as *[Orchis mascula](/source/Orchis_mascula)*, the [pollinia](/source/Pollinium) or pollen masses, are connected by [stipes](/source/Stipe_(botany)) down to [adhesive discs](/source/Viscidium) attached to the rostellum which forms cups keeping the discs or balls sticky.[2]

In the *[Catasetum](/source/Catasetum)* flower an extension of the rostellum forms a narrow feeler or "antenna" projecting forward over the labellum.

In *[Catasetum](/source/Catasetum)* flowers the rostellum projects forward at each side as an "antenna", and the pollen masses are connected by a bent stalk or [pedicel](/source/Pedicel_(botany)) to a sticky disc kept moist at the back of the flower. When an insect touches an "antenna", this releases the bent pedicel which springs straight and fires the pollinium, sticky disc first, at the insect. [Charles Darwin](/source/Charles_Darwin) described in *[Fertilisation of Orchids](/source/Fertilisation_of_Orchids)* how he "touched the antennæ of C. callosum whilst holding the flower at about a yard's distance from the window, and the pollinium hit the pane of glass, and adhered to the smooth vertical surface by its adhesive disc."[3]

## References

1. **[^](#cite_ref-ao_1-0)** Petra Ballings (2006). ["About Orchids"](https://web.archive.org/web/20090422205323/http://vumba-nature.com/about_orchids.htm). Vumba nature. Archived from [the original](http://www.vumba-nature.com/about_orchids.htm) on 2009-04-22. Retrieved 2009-08-12.

1. **[^](#cite_ref-orchids9_2-0)** [Darwin 1862](#CITEREFDarwin1862), pp. [9–19](http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F800&pageseq=20)

1. **[^](#cite_ref-orchids211_3-0)** [Darwin 1862](#CITEREFDarwin1862), pp. [211–214, \[http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F800&pageseq=237 222–224](http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F800&pageseq=226)

- Darwin, Charles (1862a), ["On the three remarkable sexual forms of *Catasetum tridentatum*, an orchid in the possession of the Linnean Society"](http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F1718&pageseq=1), *Proceedings of the Linnean Society of London*, no. Botany 6 (published 3 April 1862), pp. 151–157, retrieved 2009-02-07

- Darwin, Charles (1862), [*On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing*](http://darwin-online.org.uk/content/frameset?viewtype=text&itemID=F800&pageseq=1), London: John Murray, retrieved 2009-02-07

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Adapted from the Wikipedia article [Rostellum](https://en.wikipedia.org/wiki/Rostellum) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Rostellum?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.