**Adventive Polyembryony: Formation of an Extra Embryo**

Adventive polyembryony is the formation of multiple embryos from a single seed. It occurs when additional embryos are formed from structures other than the zygote (fertilized egg). These additional embryos can develop from the nucellus or the integument.

**Nucellus and Integument**

- The nucellus is a nutritive tissue present within the ovule of a flowering plant. It provides nourishment to the developing embryo.
- The integument is the protective covering around the ovule.

**Formation of Extra Embryo**

In adventive polyembryony, an extra embryo is formed from either the nucellus or the integument. Let's understand these processes in detail:

1. **Nucellar Polyembryony:** In this type of polyembryony, the nucellus, instead of degenerating after fertilization, continues to divide and form multiple embryos. These embryos can develop from the nucellar cells surrounding the embryo sac or from the nucellar cells adjacent to the integument.

2. **Integumentary Polyembryony:** In this type, the integument cells surrounding the embryo sac divide and develop into multiple embryos. These embryos can develop from the integument cells adjacent to the embryo sac or from the outer layers of the ovule.

**Significance of Adventive Polyembryony**

Adventive polyembryony has several ecological and evolutionary advantages:

1. **Genetic Diversity:** Producing multiple embryos enhances genetic diversity within a population, increasing its adaptability to changing environmental conditions.

2. **Vegetative Propagation:** The extra embryos formed in adventive polyembryony can germinate and develop into new plants, facilitating vegetative propagation and clonal reproduction.

3. **Enhanced Survival:** If one embryo fails to develop or survive, the presence of multiple embryos increases the chances of at least one embryo successfully developing into a mature plant.

4. **Conservation:** Adventive polyembryony can help conserve rare or endangered plant species by producing a higher number of individuals from a single seed.

In conclusion, adventive polyembryony refers to the formation of an extra embryo from the nucellus or the integument. This process enhances genetic diversity, allows for vegetative propagation, increases survival rates, and aids in the conservation of plant species.

Correct answer is B