In heterosporous pteridophytes, the development of the zygotes into young embryos take place `:
1 within the female sporophytes
2 within seed
3 within capsule
4 within the female gametophytes

Options

A. within the female sporophytes
B. within seed
C. within capsule
D. within the female gametophytes

Answer

To solve the question regarding the development of zygotes into young embryos in heterosporous pteridophytes, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Heterosporous Pteridophytes**:
- Heterosporous pteridophytes are plants that produce two different types of spores: microspores (male) and megaspores (female). Examples include Selaginella and Salvinia.

2. **Identify the Role of Spores**:
- Microspores develop into male gametophytes, while megaspores develop into female gametophytes. The female gametophyte is crucial for the fertilization process.

3. **Zygote Formation**:
- After fertilization, the zygote is formed. In heterosporous pteridophytes, the zygote develops into an embryo.

4. **Location of Zygote Development**:
- The development of the zygote into a young embryo occurs within the female gametophyte. This is where the necessary nutrients and protection are provided for the developing embryo.

5. **Evaluate the Options**:
- Option 1: Within the female sporophyte - Incorrect, as the zygote does not develop here.
- Option 2: Within seed - Incorrect, since pteridophytes are seedless.
- Option 3: Within capsule - Incorrect, as this does not pertain to zygote development.
- Option 4: Within the female gametophyte - Correct, as this is where the zygote develops.

### Final Answer:
The correct answer is **Option 4: within the female gametophytes**.