. Introduction to botany. Botany. Mosses, Ferns, and Horsetails. 297 they are neither more nor less than the sporophyte parasitic upon the gametophyte. We see that In pro- ceeding from the moss to the fern, or from a lower to a higher type of vegetation, the ga- metophyte becomes much reduced in size and complexity of structure, while the sporophyte relatively advances in these re- spects (compare shaded and unshaded portions of Figs. 157-158). Turning now to the Spermatophytes or flow- ering plants, the most complex and special- ized of plants, and the latest product of plant evolution, we fi
. Introduction to botany. Botany. Mosses, Ferns, and Horsetails. 297 they are neither more nor less than the sporophyte parasitic upon the gametophyte. We see that In pro- ceeding from the moss to the fern, or from a lower to a higher type of vegetation, the ga- metophyte becomes much reduced in size and complexity of structure, while the sporophyte relatively advances in these re- spects (compare shaded and unshaded portions of Figs. 157-158). Turning now to the Spermatophytes or flow- ering plants, the most complex and special- ized of plants, and the latest product of plant evolution, we find two kinds of spores (read paragraph 142, page 201), the pollen spores and the embryo sac spore within the ovule. The fact that the em- bryo sac is a spore is not so evident from its appearance as from its behavior. In tracing the life cycle of a fern and a moss we began with the germination of the spores, and we shall begin at. FIG. 159. Diagrams of the sporophyte and gametophytes of a flowering plant. The pollen spore (d) produced asexually on the plant (sporophyte) is the beginning of the male gametophyte, and the embryo sac spore m, also produced asexu- ally on the sporophyte, is the beginning of the female gametophyte. All of both gameto- phytes {e and n) produced by the germination of both kinds of spores is shaded; all of the sporophyte is left unshaded. There is no dif- ferentiated archegonium and antheridium on the gametophytes. 6 and c, later stages than a. The young sporophyte or embryo {o) has sprung from the fertilized egg. At/ is the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Stevens, William Chase, 1861-. Boston, D. C. Heath & Co.
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