Petals form a boat-shaped structure in papilionaceous corolla

Options

A. One, anterior
B. One, posterior
C. Two anterior
D. Two lateral.

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the structure of petals in a papilionaceous corolla, specifically how they form a boat-shaped structure.

2. **Defining Corolla**: The corolla is the second whorl of a flower, composed of petals. It serves to protect the reproductive parts of the flower, such as stamens and carpels.

3. **Identifying Papilionaceous Corolla**: A papilionaceous corolla is characterized by having five petals that are often free and resemble a butterfly. This type of corolla is typical in the family Fabaceae (legumes).

4. **Analyzing the Petal Arrangement**: In a papilionaceous corolla, the petals are arranged as follows:
- One larger petal at the top, known as the "standard" or "banner."
- Two lateral petals known as "wings."
- Two lower petals that are fused together to form a structure resembling a boat, often referred to as the "keel."

5. **Identifying the Boat-Shaped Structure**: The boat-shaped structure in the papilionaceous corolla is formed by the two interior petals, which are fused at the base. This structure is crucial for the flower's reproductive processes.

6. **Conclusion**: Therefore, the correct answer to the question is that the two interior petals form the boat-shaped structure in the papilionaceous corolla.

### Final Answer:
The two interior petals form the boat-shaped structure in papilionaceous corolla.

---