The Angiospermae

Angiospermae, also called angiosperms, are the flowering plants. Flowers, when fertilised, produce fruit containing seeds.

The only other seed-producing group, the Gymnospermae or gymnosperms, produce seeds in cones.

Both angiosperms and gymnosperms are spermatophytes (seed-producing), but only angiosperms produce flowers and fruit, and fruits only form from fertilised flowers.

The jujube tree, Ziziphus jujuba Mill. is an angiosperm.

Flowers

Flowers are the sex organs of angiosperms, and can be male, female, or both (hermaphroditic).

Male and the male part of hermaphroditic flowers produce pollen (comprised of sperm-containing pollen grains), and female and the female part of hermaphroditic flowers produce ovules (comprised of egg cells).

Flowers are arranged in one of three ways, and a species is characterised by this arrangement. A species will always have:

• hermaphroditic flowers on the same plant, or
• both male-only and female-only flowers on the same plant, or
• male-only and female-only flowers on individual plants

The following illustration shows these three different arrangements:

Dioecious Species

Dioecious species are those with distinct male-only and female-only plants. While about 65% of gymnosperms are dioecious, only about 6% of angiosperms are. Male-only angiosperms produce male-only flowers and female-only angiosperms produce female-only flowers. Dioecious angiosperms thus produce unisexual flowers. An example of a dioecious angiosperm is the weeping willow (Salix babylonica).

Monoecious Species

Monoecious species are those with either distinct male and female sex organs on the same plant, or, specifically in the case of angiosperms, flowers on the same plant with both male and female parts.

As with dioecious angiosperms, the flowers on monoecious angiosperms which are either male or female are also unisexual flowers. The flowers on monoecious species which contain both male and female parts are called bisexual, hermaphroditic, or perfect flowers.

The jujube tree, Ziziphus jujuba Mill.

The jujube tree Ziziphus jujuba Mill. is a monoecious species, and its flower is a perfect flower.