Here's why:

* Ferns: Ferns have a life cycle that alternates between a sporophyte (the familiar leafy plant) and a gametophyte (a small, heart-shaped structure). The sporophyte produces spores in structures called sporangia, which are usually located on the underside of the fronds.

* Mosses: Mosses also have a life cycle that alternates between a sporophyte (a stalk with a capsule at the top) and a gametophyte (the leafy green plant). The sporophyte produces spores in the capsule.

Seeds, on the other hand, are produced by flowering plants (angiosperms) and gymnosperms (conifers, cycads, ginkgoes). Seeds contain a miniature plant embryo, food supply, and protective coat.