A vesselless piece of stem possessing prominent sieve tubes would belong to

Options

A. Pinus
B. Eucalyptus
C. Grass
D. Trochodendron

Explanation

To determine which group of plants a vessel-less piece of stem with prominent sieve tubes belongs to, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Key Terms**: The question mentions "vessel-less" and "prominent sieve tubes." This indicates we are looking for a plant group that lacks xylem vessels but has well-developed phloem with sieve tubes.

2. **Analyze Pteridophytes**: Pteridophytes (ferns and their relatives) do not have true xylem vessels. However, they also do not possess prominent sieve tubes in their phloem. Therefore, pteridophytes can be eliminated as an option.

3. **Examine Gymnosperms**: Gymnosperms (like conifers) have xylem that lacks vessels but have tracheids instead. While they do have phloem, it typically consists of sieve cells rather than prominent sieve tubes. Thus, gymnosperms can also be ruled out.

4. **Consider Angiosperms**: Angiosperms (flowering plants) are characterized by having both xylem vessels and phloem with prominent sieve tubes. However, there are primitive dicots within angiosperms that may lack vessels.

5. **Identify Primitive Angiosperms**: An example of a primitive dicot that lacks vessels is *Trochodendron*. This plant has prominent sieve tubes in its phloem but does not have xylem vessels.

6. **Conclusion**: Based on the analysis, the vessel-less piece of stem with prominent sieve tubes would belong to a primitive dicot, specifically *Trochodendron*.

### Final Answer:
A vessel-less piece of stem possessing prominent sieve tubes would belong to *Trochodendron*, a primitive dicot in the angiosperms.

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