The flowers are male, having stamens but no carpels.


The flowers are female, having carpels but no stamens.


Every flower on the plant has both male (stamens) and female (carpels) structures. Alternative names for bisexual are: androgynous, hermaphroditic, monoclinous and synoecious. Recent studies in the likely most recent ancestral flower of angiosperms suggests that the most recent ancestral flower was bisexual, and that unisexual flowers evolved independently many times afterwards. (The ancestral flower itself is at the moment as elusive as ever).


The plant can be either Monoecious or Dioecious, see below.


Many plants are Monoecious, that is have separate male and female flowers where both occur on the same plant. Monoecious plants can pollinate each other and (probably) themselves too.


Much fewer plants are Dioecious where separate male and female flowers are on separate plants.

This has reproduction implications: both male and female plants need to be nearby in order for fertilization of female flowers by male flowers to occur. If fertilization does not occur, a female plant will not produce fruit or berries (but a male plant will always produce pollen). In dioecious plants it is generally that the male flowers last much longer than the female flowers which turn to fruit soon after being fertilised. The male flowers just keep on going ready to fertilise other female plants of the species.


Having both bisexual, male and female flowers on the same plant. Alternative names for polygamous are androgynomonoecious, polygamomonoecious and trimonoecious.


Having both bisexual/hermaphrodite and female flowers on the same plant.


Having a mixture of bisexual/hermaphrodite flowers on some plants and only female flowers on other plants. These might include male plants, sterile plants (male sterile or female sterile) and hermaphrodite plants - and a little-known fourth class of partially male sterile plants where temperature influences sexual expression and the degree of male sterility but not in the former 3 classes. Examples of gynodioecious flowers include Buck's-horn Plantain, Bladder Campion, Devil's-bit Scabious and Meadow Saxifrage


Having both bisexual and male flowers on the same plant.


Having bisexual and male flowers on separate plants.




Heterostylous - having two forms of bisexual flower: Pin and Thrum, either of which can only fertilise the opposite form. Pin forms have a long style and short stamens, whereas thrum forms have long stamens and a short style. Because the pin and thrum forms are determined by genes, the same plant has either all pin flowers or all thrum flowers (the Author thinks). See Primrose for a much fuller explanation and for information on further forms.

Purple Loosestrife takes heterostyly to the third level where there are three types of flower morphs. It is thus Tristylous. Each flower morph has two types of stamens (but only one stigma). The two types of stamens are in sets of (nominally) six each. The first morphological type where the style is short and the two stamens are medium and long; the second morph has a medium length style and long and short stamens; the third morph has a long style with medium and short stamens. Pollen transferred from flowers of the same morph will not result in fertilization because the individual morphs are self-incompatible. The three flower morphs are adapted to pollination by different insects. Generally, pollen from the stamen nearest to the stigma will pollinate the stigma.

Plant sexuality is not always so straightforward, there are many half-way houses and permutations on the above.  Plant Reproductive Morphology


  • 'EOR' or '⊕' is the Logical 'Exclusive OR' (sometimes spelled 'EXOR' or 'XOR') being 'either one or the other', but not both.
  • '&' is the Logical 'AND' meaning both at the same time.

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