Allogamy is also called cross-pollination which is favoured by Dicliny i.e., the presence of a separate male (staminate) and female (pistillate) flowers on the same plant.

The correct answer is option 'C' - Dicliny.

Dicliny refers to the condition in which the male and female reproductive structures are present in separate flowers on the same or different plants. This condition favors allogamy, which is the process of cross-fertilization between different individuals. Let's understand why dicliny is best favored by allogamy.

1. Dicliny and Allogamy:
- Dicliny, also known as unisexuality, ensures that male and female reproductive structures are present in separate flowers. This separation reduces the chances of self-fertilization.
- Allogamy, on the other hand, refers to the cross-fertilization between different individuals. It promotes genetic diversity and reduces the risk of inbreeding depression.
- When male and female reproductive structures are present in separate flowers, the chances of cross-pollination between different individuals increase, thereby favoring allogamy.

2. Advantages of Allogamy:
- Genetic diversity: Allogamy promotes the exchange of genetic material between different individuals. This genetic diversity is beneficial for populations as it increases the chances of survival and adaptation to changing environments.
- Reduced inbreeding depression: Inbreeding depression occurs when closely related individuals mate, leading to the expression of harmful recessive alleles. Allogamy helps to avoid this by promoting outbreeding.
- Enhanced reproductive success: Cross-fertilization allows for greater genetic recombination, resulting in offspring that may have improved fitness and adaptability.

3. Other options:
- Chasmogamy: Chasmogamy refers to the condition where flowers are open and exposed, allowing for cross-pollination. While chasmogamy can promote allogamy, it is not the best option as it does not guarantee cross-fertilization between different individuals.
- Cleistogamy: Cleistogamy refers to the condition where flowers remain closed, leading to self-fertilization. This condition is not favorable for allogamy as it promotes self-fertilization and limits genetic diversity.
- Homogamy: Homogamy refers to the condition where flowers of the same plant are self-pollinated or cross-pollinated. It does not involve cross-fertilization between different individuals, making it less favorable for allogamy.

In conclusion, dicliny, which involves separate male and female flowers on the same or different plants, is best favored by allogamy. This combination allows for cross-fertilization between different individuals, promoting genetic diversity and reducing the risk of inbreeding depression.

When the fertilization of an ovum in a flower occurs by the spermatozoa of another flower, such a mechanism is called allogamy. It is facilitated in conditions where the flower has only one type of gamete, be it male or female. Complete answer: Allogamy is best favoured by dicliny.