The sporophyte of seed plants, or the "plant" as we know it, produces two kinds of spores—one kind becoming pollen-grains and the other kind embryo-sacs. The pollen-spores are borne in sporangia, which are united into what are called anthers. The embryo-sac, which contains the egg-cell, is borne in a sporangium known as an ovule. A gametophytic stage is present in both pollen and embryo sac: fertilization takes place, and a sporophyte arises. Soon this sporophyte becomes dormant, and is then known as an embryo. The embryo is packed away within tight-fitting coats, and the entire body is the seed. When the conditions are right the seed grows, and the sporophyte grows into herb, bush, or tree. The utility of the alternation of generations is not understood.
The spores of ferns are borne on leaves; the spores of seed-bearing plants are also borne amongst a mass of specially developed conspicuous leaves known as flowers, therefore these plants have been known as the flowering plants. Some of the leaves are developed as envelopes (calyx, corolla), and others as spore-bearing parts, or sporophylls (stamens, pistils). But the spores of the lower plants, as of ferns and mosses, may also be borne in specially developed foliage, so that the line of demarcation between flowering plants and flowerless plants is not so definite as was once supposed. The one definite distinction between these two classes of plants is the fact that one class produces seeds and the other does not. The seed-plants are now often called spermaphytes, but there is no single coördinate term to set off those which do not bear seeds. It is quite as well, for popular purposes, to use the terms phenogams for the seed-bearing plants and cryptogams for the others. These terms have been objected to in recent years because their etymology does not express literal facts
