In Mirabilis the achene is covered by hardened remains of calyx. Such an achene is called

Options

A. Nut
B. Caryopsis
C. Scleranthium
D. Cypsela.

Answer

To answer the question, "In Mirabilis, the achene is covered by hardened remains of calyx. Such an achene is called," we will follow these steps:

### Step-by-Step Solution:

1. **Understand the Term "Achene":**
- An achene is a type of dry fruit that contains a single seed. It is characterized by its hard outer wall, which is derived from the ovary wall (pericarp).

2. **Identify the Characteristics of the Achene in Mirabilis:**
- In the case of Mirabilis, the achene is specifically noted to be covered by hardened remains of the calyx. This is an important detail that will help us identify the correct term.

3. **Examine the Options Provided:**
- The options given are:
- a) Narth
- b) Caryopsis
- c) Scleranthium
- d) Crypsela

4. **Analyze Each Option:**
- **Narth:** Not a commonly recognized term in botany related to fruits.
- **Caryopsis:** This is a type of dry, one-seeded fruit where the seed coat is fused with the ovary wall, commonly found in grasses. This does not match the description for Mirabilis.
- **Scleranthium:** This term refers to a type of achene that is covered by hardened calyx remains, which fits the description for Mirabilis.
- **Crypsela:** This is a dry, single-seeded fruit formed from a double ovary, typically found in daisies. This does not apply to Mirabilis.

5. **Conclusion:**
- Based on the analysis, the correct answer is **Scleranthium**, as it matches the description of an achene covered by hardened remains of the calyx in Mirabilis.

### Final Answer:
The achene covered by hardened remains of calyx in Mirabilis is called **Scleranthium**.