Spermatophytes in the context of "Testa (botany)"

In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a testa. More generally, the term "seed" means anything that can be sown, which may include seed and husk or tuber. Seeds are the product of the ripened ovule, after the embryo sac is fertilized by sperm from pollen, forming a zygote. The embryo within a seed develops from the zygote and grows within the mother plant to a certain size before growth is halted.

The formation of the seed is the defining part of the process of reproduction in seed plants (spermatophytes). Other plants such as ferns, mosses and liverworts, do not have seeds and use water-dependent means to propagate themselves. Seed plants now dominate biological niches on land, from forests to grasslands both in hot and cold climates.

The euphyllophytes are a clade of plants within the tracheophytes (the vascular plants). The group may be treated as an unranked clade, a division under the name Euphyllophyta or a subdivision under the name Euphyllophytina. The euphyllophytes are characterized by the possession of true leaves ("megaphylls"), and comprise one of two major lineages of extant vascular plants. As shown in the cladogram below, the euphyllophytes have a sister relationship to the lycopodiophytes or lycopsids. Unlike the lycopodiophytes, which consist of relatively few presently living or extant taxa, the euphyllophytes comprise the vast majority of vascular plant lineages that have evolved since both groups shared a common ancestor more than 400 million years ago. The euphyllophytes consist of two lineages, the spermatophytes or seed plants such as flowering plants (angiosperms) and gymnosperms (conifers and related groups), and the Polypodiophytes or ferns, as well as a number of extinct fossil groups.

The division of the extant tracheophytes into three monophyletic lineages is supported in multiple molecular studies. Other researchers argue that phylogenies based solely on molecular data without the inclusion of carefully evaluated fossil data based on whole plant reconstructions, do not necessarily completely and accurately resolve the evolutionary history of groups like the euphyllophytes.