How does the reproduction of seedless plants differ from that of seed plants?

They produce via spores. Same goes with the seedless vascular plants (spike mosses, club mosses, horsetails, whisk ferns, true ferns) The " seed " plants are the gymnosperms and the angiosperms.

Seedless plants produce spores. Spores can develop into an adult without fusing with another cell. Seed plants produce seeds. Seeds are formed when the female reproductive structure matures; this occurs after fertilization.