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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, stamen 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 such as those found in toyon, where as some are saucer-shaped as found 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, this is where the ovary is below the other attached floral parts. The hypanthium is known by different common names in differing species, such as the case with the eucalypts, it is referred to as the gum nut.

Variations in plant species[edit]

In myrtles the hypanthium or the floral tube that surrounds the ovary, it can either surround the ovary loosely or tightly, in some cases it can be fussed to the walls of the ovary and 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 where the sepals, petals and stamens all arise from. In the rosaceae family or more commonly the rose family the hypanthium is lined with nectar producing tissue known as nectaries. This nectar is the source of the pollen that is used for pollinating related plants. The nectar is a sugary substance that attracts birds and bees to the flower and they then take the pollen from the lining of the hypanthium and transfer it to the next flower they visit, this is usually a neighbouring plant.[2]

The stamen that is encapsulated by the hypanthium it is the pollen producing reproductive organ of the flower. It usually consists of a filament - the male organ and an anther – the female organ. The Anthers are typically two lobed and attaches 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. This is done via the hypanthium providing weather protection and a medium to sustain the lost pollen. This is beneficial in the reproduction process, because it increase probability of fertility and cross pollination between the plant species.[4] The retained pollen can then attach to pollinators such as birds, bees, moths, beetles, bats, butterflies and other animals, also wind can act as an instigator for fertilisation. The hypanthium is also an adaptive feature for structural support. This helps the stem fuse together with the flower, in turn strengthening the bond and overall plants 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