Multicellular fragment of a blue green alga capable of growth into new plant is

Options

A. Hormocyst
B. Trichome
C. Trichogyne
D. Hormogonium.

Answer

**Step-by-Step Solution:**

1. **Understanding the Organism**: The question refers to a multicellular fragment of a blue-green alga. Blue-green algae are scientifically known as cyanobacteria, which are photosynthetic prokaryotes.

2. **Reproduction in Cyanobacteria**: Cyanobacteria primarily reproduce asexually. One of the common methods of asexual reproduction in these organisms is through fragmentation.

3. **Fragmentation Process**: During fragmentation, the thallus (the body) of the cyanobacteria breaks into smaller pieces. These pieces are capable of developing into new organisms.

4. **Identification of the Fragment**: The specific term used for these multicellular fragments that can grow into new plants is "hormogonia" (singular: hormogonium).

5. **Growth Potential**: Each hormogonium can grow into a new filament of cyanobacteria, thus allowing for the continuation of the species.

6. **Conclusion**: Therefore, the multicellular fragment of a blue-green alga capable of growth into a new plant is called a "hormogonium".

**Final Answer**: Hormogonium

---