Which layer in Arceuthobium has fibrous thickening and it is called?

Options

A. Exothecium
B. Endothecium
C. Middle layer
D. Tapetum

Answer

To answer the question regarding which layer in Arceuthobium has fibrous thickening, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Structure**: Recognize that Arceuthobium, commonly known as an anther, consists of four distinct layers: Exothasium, Endothasium, Middle layer, and Tapetum.

2. **Analyze Each Layer**:
- **Exothasium**: This is the outermost layer of the anther. It is characterized by its toughness and the presence of fibrous thickening. The fibers in this layer are primarily made up of cellulose, which provides protection to the anther.
- **Endothasium**: This layer is a single layer made of pectin. Its primary function is to protect the inner pollen grains until they mature.
- **Middle Layer**: This layer acts as a partition between the endothasium and exothasium and is known for its stretchable condition.
- **Tapetum**: This layer is responsible for providing nutrition to the developing pollen grains.

3. **Conclusion**: Based on the analysis, the layer that exhibits fibrous thickening is the **Exothasium**. This layer not only serves as the outer protective layer but also contributes to the structural integrity of the anther through its fibrous composition.

### Final Answer:
The layer in Arceuthobium that has fibrous thickening is called the **Exothasium**.

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