In Primula, cross pollination is favoured by

Options

A. Herkogamy
B. Dichogamy
C. Heterostyly
D. Dicliny.

Answer

To solve the question "In Primula, cross-pollination is favoured by," we need to analyze the options provided and understand the reproductive characteristics of Primula flowers. Here's a step-by-step breakdown of the solution:

### Step 1: Understand the Types of Flowers in Primula
Primula has two types of flowers:
- **Pin flowers** (Pinnate): These have long stamens and short stigmas.
- **Thrum flowers** (Thermite): These have short stamens and long stigmas.

### Step 2: Analyze the Mechanism of Cross-Pollination
The difference in the lengths of the stamens and stigmas in the two types of flowers promotes cross-pollination. The pin flowers and thrum flowers are structured in such a way that they encourage pollen transfer between different flowers, rather than self-pollination.

### Step 3: Evaluate the Options
1. **Helicogamy**: This refers to a mechanism where the flower prevents the male and female reproductive parts from meeting, which does not favor cross-pollination.

2. **Dichogamy**: This is a condition where the male and female parts of the flower mature at different times. While this can prevent self-pollination, it does not specifically promote cross-pollination in the context of Primula.

3. **Heterostyly**: This is the condition where flowers have different styles (lengths of the stigma) and stamens. In Primula, the presence of both pin and thrum flowers exemplifies heterostyly, which encourages cross-pollination.

4. **Declining**: This term is not relevant in the context of promoting cross-pollination.

### Step 4: Conclusion
Based on the analysis, the option that best describes the mechanism that favors cross-pollination in Primula is **Heterostyly**.

### Final Answer
**Option 3: Heterostyly**

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