Angiosperms

These have special structures flowers and fruits which were absent in previous divisions. These are known as flowering plants (Fig.1).

Flowers:

It is a structure that is needed for sexual reproduction. It has four parts:
1. Calyx- This is a whorl formed by green leaf-like structures growing at the base of the petals known as sepals. The main function of the calyx and its sepals is to protect the flower before it blossoms(in the bud stage)
2. Corolla- This is present inner to the calyx and is formed of coloured leaf-like structures known as petals. The colour helps to attract pollinators.
3. Carpel (Gynoecium)- These are megasporophylls that is, produce female gamete, egg. It is formed of stigma, style and ovary. Stigma is a flat receptor to receive the pollens that come from pollination. The ovary is an oval structure that contains ovule/ovules which develop into seeds. Style is a thin structure that connects stigma with the ovary. The carpel is also known as the pistil. There can be single or multiple carpels in flower.
4. Stamens (Androceium)- The are microsporophylls i.e. produce male gamete, pollen grains. It is formed of thin stalk-like structures known as filaments and a sac known as anther. The haploid pollen grains are formed in the anther.

Fruits:
After fertilisation, the ovule develops into a seed and the ovary develops into a fruit.

Sexual reproduction in angiosperms.

The angiosperms have megasporangium and microsporangium in flower. The megasporangium is present in the carpel which has the female gametophyte (embryo sac). It contains egg. The microsporangium produces pollen grains that contain sperms. When the pollen grain land on the stigma by pollination, a pollen tube is formed. The sperms pass through it to reach the egg and fertilise. This forms the zygote which develops into an embryo. The ovule develops into a seed in which embryo is present. When it reaches the ground, it grows to form a new plant.

The angiosperms have a single phylum known as anthrophyta which is divided into three groups: basal angiosperms, monocots and eudicots.

1. Basal angiosperms- These are tall trees with undifferentiated petals and sepals. A receptacle is present that is cone-shaped. It has stamens at the bottom and capel at the top. Example: Magnolia, water lily, and avocado tree.
2. Monocots- These have only one cotyledon in their seeds. Example: Maize, corn and wheat.
3. Eudicots- These have two cotyledons. More than 2/3rd of the angiosperm belong to this group. Example: Oak, maple and peaches.