spermatophyte

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spermatophyte

any plant of the division Spermatophyta, comprising all forms of seed-bearing plants, ANGIOSPERMS and GYMNOSPERMS.
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doubt, widespread zooidogamy among ancient seed plants.
1951), which is on the stem lineage of the extant seed plants (Nixon et
multispermy) in Microcycas among extant seed plants is thus an
autapomorphy of Microcycas within extant seed plants (Fig.
Our work has shown that oleanane is lacking from a wide range of fossil plants," he notes, "but the chemical is found in Permian sediments containing extinct seed plants called gigantopterids.
That makes gigantopterids the oldest oleanane-producing seed plants on record--an indication that they were among the earliest relatives of flowering plants, concludes biologist David Winship Taylor of Indiana University Southeast, New Albany, a co-author of the study.
Nevertheless, only a few studies (Coulter 1914; Eames 1961; Takhtajan 1972, 1976; Stebbins 1974; Favre-Duchartre 1978, 1979, 1984; Friedman 1987a,b, 1993; Choi and Friedman 1991; Takhtadzhian 1991; Friedman and Gifford 1997) have focused explicitly on the developmental and evolutionary bases for structural variation among male and female gametophytes of seed plants.
Extant seed plants comprise five clades [ILLUSTRATION FOR FIGURE 1 OMITTED]: cycads, Ginkgo, conifers, angiosperms, and Gnetales (Ephedra, Welwitschia, Gnetum).
In most nonflowering seed plants (cycads, Ginkgo, conifers, Ephedra), this cellularization phase is succeeded by a period of additional growth and development, during which two or more female gametangia (each with a single egg cell) are formed.
It presents identification keys to more than 4,200 taxa of pteridophytes and seed plants that are native or naturalized in Florida.
Endozoochory is common for seed plants, but its usefulness for other taxa is largely unknown.
The newly found fossil might represent the first evidence of an intermediate stage between pteriodphytes and early seed plants.