Cleistogamy is found in flowers of Commelina species, which remains underground and closed all their life.

New varieties cannot be obtained by self pollination.

Dichogamy is the condition in which the timing of maturation of andorecium and gynoecium are different.

Cross pollination is not economical because the flowers have to adapt themselves to attract pollinating agents.

In some plants (such as sweet pea, salvia), anthers of the flower mature earlier than the stigma. This condition is known as protandry.

In peepal plant, stigma matures earlier than the anther. This condition is known as protogany.

In vallisneria, the pollination occurs through water.

In some plants like apples and grapes, pollen grains of a flower fail to fertilise the flower of the same plant, but fertilise the stigma of the flower borne by another plant of the same species.

In herkogamy, anther and stigma are so placed in a flower that the pollen grains are unable to reach the stigma in the same flower.

Salvia is a bisexual flower.

In heterostyly, the length of style and the position of anthers are different in a flower.

Gloriosa shows herkogamy as in this plant, the pollen grains are liberated towards outside of the flower for preventing them from reaching the stigma of the same flower.

Plants are dioecious, i.e. male and female flowers borne on separate plants.

Entomophily is the pollination of flowers by insects.

Endosperm is a food-storing tissue, which is formed by the fusion of the male gamete and two polar nuclei.

Petals are large and brightly coloured to attract the insects for pollination.

Pine is usually pollinated by wind.

Endosperm in plants is 3n as it is formed by the fusion of male gamete (1n) and secondary nucleus (2n).

The embryo sac contains an egg and two polar nuclei.

Two male gametes are present in a pollen tube. One fuses with the egg and the other fuses with two polar nuclei to form endosperm.