Where does the spore formation occur in cellular slime mould?

The correct option is Sporangium.

Step-by-step Explanation:

1. Understanding Cellular Slime Moulds:
Cellular slime moulds exist as individual, free-living amoeboid cells in the soil when nutrients are plentiful. However, when food runs out, they initiate a cooperative social cycle by aggregating together.

2. Aggregation and Pseudoplasmodium:
The individual cells aggregate in response to chemical signals (specifically cyclic AMP) to form a multicellular, slug-like structure called a pseudoplasmodium. Within this aggregate, the individual cells retain their cell membranes and distinct cellular identities, unlike the single multinucleate mass of protoplasm (plasmodium) found in acellular slime moulds.

3. Differentiation of the Fruiting Body:
The migrating pseudoplasmodium eventually halts and reorganizes to form a reproductive structure known as a fruiting body (or sorocarp). This structure differentiates into two distinct parts:
- Sporophore: The supportive multicellular stalk.
- Sporangium: The capsule or head located at the top of the stalk.

4. Site of Spore Formation:
Cells within the upper capsule-like structure, the sporangium, differentiate and develop into rugged, dormant spores (encystment). Once mature, the sporangium releases these spores into the environment, where they germinate into new amoeboid cells under favorable conditions.