Middle layers of pollen sac wall are absent in

Options

A. Compositae
B. Lemnaceae
C. Najadaceae
D. Both B and C.

Answer

To solve the question "Middle layers of pollen sac wall are absent in?", we can follow these steps:

### Step 1: Understand the Structure of Pollen Sac
The pollen sac, or microsporangium, has several layers:
- **Epidermis**: The outer protective layer.
- **Endothecium**: The layer beneath the epidermis.
- **Middle layers**: Typically 2 to 3 layers that may store food.

### Step 2: Identify the Options
The options provided are:
- A) Composite
- B) Lamnaceae
- C) Nanjadesi
- D) Both B and C

### Step 3: Analyze Each Option
- **Composite**: This family has 2-3 middle layers in the pollen sac wall. Therefore, it does not fit the criteria.
- **Lamnaceae**: This family is known to lack middle layers in the pollen sac wall. This option fits the criteria.
- **Nanjadesi**: Similar to Lamnaceae, this family also lacks middle layers in the pollen sac wall. This option also fits the criteria.

### Step 4: Conclusion
Since both Lamnaceae and Nanjadesi lack middle layers in the pollen sac wall, the correct answer is:
**D) Both B and C.**