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In angiosperms the fusions of two floral parts or adnation is referred to as the hypanthium. The hypanthium is where the calyx, stamens and a partly fused portion of the corolla forms a cup shaped tube that surrounds the carpels. It can often contain the nectar or pollen of the plant. It is present in most flowering species, although can slightly vary in structural dimensions and appearance.[1] This differentiation between the hypanthium in particular species is useful with identification. Some geometric forms are obconic shapes asit in toyon, whereas some are saucer-shaped as in some species of the genus Mitellastra.

Its presence is diagnostic of many families, including the Rosaceae, Grossulariaceae, and Fabaceae. In some cases, it can be so deep, with such a narrow top, that the flower can appear to have an inferior ovary - the ovary is below the other attached floral parts. The hypanthium is known by different common names in differing species. For example, in the eucalypts, it is referred to as the gum nut.

Variations in plant species[edit]

In myrtles the hypanthium can either surround the ovary loosely or tightly; in some cases it can be fused to the walls of the ovary. It can vary in length. The rims around the outside of the hypanthium contain the calyx lobes or free sepals, petals and either the stamen or multiple stamen that are attached at one or two points. The flowers of the Rosaceae family always have some type of hypanthium or at least a floral cup from which the sepals, petals and stamens all arise. In the Rosaceae family, or the rose family, the hypanthium is lined with nectar-producing tissue known as nectaries. The nectar is a sugary substance that attracts birds and bees to the flower, who then take the pollen from the lining of the hypanthium and transfer it to the next flower they visit, usually a neighbouring plant.[2]

The stamens borne on the rim of the hypanthium are the pollen-producing reproductive organs of the flower. The androecious or male organ usually consists of a filament which is a structure that supports the anther, which release the pollen. The anthers are typically two-lobed and attach to the filament either at the base or middle.[3] The hypanthium helps in many ways with the reproduction and cross pollination pathways of most plants. It provides weather protection and a medium to sustain the lost pollen, increasing the probability of fertility and cross-pollination.[4] The retained pollen can then attach to pollinators such as birds, bees, moths, beetles, bats, butterflies and other animals. Wind can act as an instigator for fertilisation. The hypanthium is also an adaptive feature for structural support. It helps the stem fuse together with the flower, in turn strengthening the bond and overall stability and integrity.[3]



  • Cronquist, Arthur (1981), An integrated system of classification of flowering plants, Columbia University Press, ISBN 978-0-231-03880-5 
  • Givnish, Thomas J; Sytsma, Kenneth Jay (1997), Molecular evolution and adaptive radiation, Cambridge University Press, ISBN 978-0-521-57329-0 
  • Snow, Neil Wilton; Guymer, Gordon P; Sawvel, G (2003), Systematics of Austromyrtus, Lenwebbia, and the Australian species of Gossia (Myrtaceae), American Society of Plant Taxonomists, ISBN 978-0-912861-65-4 
  • Snow, Neil Wilton; Guymer, Gordon P; Sawvel, G (2003), Systematics of Austromyrtus, Lenwebbia, and the Australian species of Gossia (Myrtaceae), American Society of Plant Taxonomists, ISBN 978-0-912861-65-4 
  • Faegri, Knut; Iversen, Johannes, 1904- (1975), Textbook of pollen analysis (3rd rev. ed ed.), Hafner Press, retrieved 8 November 2013 
  • Clarke, Andrew. GM crops : science, agriculture and potential legal issues; Lunney, Mark. What Australian courts might say about "damage" from cross-pollination by a GMO; University of New England. Australian Centre for Agriculture and Law (2004), On agriculture and biotechnology, Marketing and Public Affairs for the Australian Centre for Agriculture and Law, University of New England, ISBN 978-1-86389-873-7 

Line notes[edit]

External links[edit]

  • Hypanthium images on MorphBank, a biological image database