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Plant anatomy

    Figure 16: Typical angiosperm life cycle (see text).

    Encyclopædia Britannica, Inc.
  • Figure 11: Floral structures characteristic of angiosperms.

    Figure 11: Floral structures characteristic of angiosperms.

    Encyclopædia Britannica, Inc.


    Encyclopædia Britannica, Inc.
  • Some of the different ways plants are pollinated.

    Some of the different ways plants are pollinated.

    Encyclopædia Britannica, Inc.

Learn about this topic in these articles:



Tradescantia ohiensis, known variously as the bluejacket or Ohio spiderwort.
Stamens (microsporophylls) are structures that produce pollen in terminal saclike structures (microsporangia) called anthers. The number of stamens comprised by the androecium is sometimes the same as the number of petals, but often the stamens are more numerous or fewer in number than the petals. There are generally two pairs of spore-containing sacs (microsporangia) in a young stamen; during...
A transverse section of the anther reveals four areas of tissue capable of producing spores. These tissues are composed of microsporocytes, which are diploid cells capable of undergoing meiosis to form a tetrad (four joined cells) of haploid microspores. The microspores become pollen grains and may eventually separate.
Weeping willow (Salix babylonica).
...Flowers that lack one or both of the above perianth parts are called incomplete. Stamens (collectively called the androecium) are the male parts of the flower. Stamens are composed of saclike anthers (microsporangia) and filaments, which are stalks that support the anthers. Anthers are usually compartmentalized and contain the pollen grains (microgametophytes). The pistil, or female part...


(Left) Generalized flower with parts; (right) diagram showing arrangement of floral parts in cross section at the flower’s base
...numerous microspores (potential pollen grains); the pistil bears ovules, each enclosing an egg cell. When a microspore germinates, it is known as a pollen grain. When the pollen sacs in a stamen’s anther are ripe, the anther releases them and the pollen is shed. Fertilization can occur only if the pollen grains are transferred from the anther to the stigma of a pistil, a process known as...


Epiphytic orchids (Dendrobium).


Common carder bumblebee (Bombus pascuorum) pollinating a honeysuckle (Lonicera species) flower.
...out in spring, or the flowers may be placed very high on the plant. Inflorescences, flowers, or the stamens themselves move easily in the breeze, shaking out the pollen, or the pollen containers ( anthers) burst open in an explosive fashion when the sun hits them, scattering the pollen widely into the air. The stigmas often are long and divided into arms or lobes, so that a large area is...
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