Pteridophytes and Bryophytes differ in having

The correct option is conducting system.

To understand why this is the correct answer, we can look at the main characteristics of Bryophytes and Pteridophytes and compare them step-by-step:

1. Presence of a Conducting System (Vascular Tissue):
The primary evolutionary difference between Bryophytes and Pteridophytes lies in their internal transport systems. Pteridophytes are vascular plants, meaning they possess a well-developed conducting system containing specialized tissues: xylem (for conducting water and minerals) and phloem (for conducting organic nutrients). This allows pteridophytes to grow taller and survive in a wider range of terrestrial habitats. In contrast, Bryophytes are non-vascular plants that lack true xylem and phloem, relying on simple diffusion and cell-to-cell transport, which limits their size.

2. Analyzing the Other Options (Shared Features):
The other options list traits that are common to both groups:
- Spermatozoids: Both Bryophytes and Pteridophytes produce motile, flagellated male gametes called spermatozoids (or antherozoids) that require water to swim to the egg.
- Archegonia: Both groups are classified as archegoniates because they develop multicellular, flask-shaped female reproductive organs called archegonia.
- Separate gametophytes: Both groups exhibit an alternation of generations where the gametophyte phase exists as a distinct, independent stage in the life cycle (though the dominance of the stages differs; the gametophyte is dominant in Bryophytes, whereas the sporophyte is dominant in Pteridophytes).

Therefore, the presence of a conducting system is the key feature that distinguishes Pteridophytes from Bryophytes.