1. Seeds: This is the defining feature! Seed plants produce seeds, which are embryos enclosed in a protective coat. Seeds allow for dispersal and provide nourishment for the developing embryo.

2. Vascular Tissue: Seed plants possess a vascular system consisting of xylem (for water transport) and phloem (for nutrient transport). This allows them to grow tall and efficiently distribute resources throughout their bodies.

3. Independent Sporophyte: The dominant stage in the life cycle of seed plants is the sporophyte generation, the plant itself. The gametophyte (the reproductive stage) is reduced and dependent on the sporophyte for its survival.

4. Heterospory: Seed plants produce two types of spores: microspores, which develop into male gametophytes, and megaspores, which develop into female gametophytes. This allows for more efficient reproduction and the evolution of pollen.

Let me know if you'd like to explore any of these characteristics in more detail!