Rhizoids in Riccia are

Options

A. Unicellular smooth
B. Unicellular smooth and tuberculate
C. Multicellular smooth and tuberculate
D. Multicellular tuberculate.

Answer

### Step-by-Step Solution:

1. **Understanding Rhizoids**:
- Rhizoids are root-like structures found in certain plants, including liverworts like Riccia. They serve primarily to anchor the plant to the substrate.

2. **Identifying Riccia**:
- Riccia is a genus of liverworts, which are non-vascular plants categorized under the division Bryophyta. Understanding the classification helps in knowing the characteristics of the plant.

3. **Location of Rhizoids**:
- In Riccia, rhizoids are located in the midrib region of the thallus (the body of the liverwort). This is important as it indicates their functional role in anchoring.

4. **Nature of Rhizoids**:
- Rhizoids in Riccia are primarily unicellular and unbranched. This means they consist of a single cell and do not have branching structures.

5. **Types of Rhizoids**:
- There are two types of rhizoids in Riccia:
- Smooth-walled rhizoids
- Tuberculate rhizoids (which have small, wart-like projections)

6. **Evaluating Options**:
- The question provides multiple-choice options regarding the nature of rhizoids in Riccia.
- Since we established that rhizoids are unicellular, we can eliminate any options that mention multicellular structures.

7. **Final Answer**:
- The correct option is that rhizoids in Riccia are "unicellular smooth and tuberculate," as they can be of both types.

### Final Answer:
Rhizoids in Riccia are unicellular smooth and tuberculate.

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