Flowers, the means of reproduction; Ovules surrounded by two integuments. Double fertilization, which leads to formation of polyploid endosperm tissue. Gnetophyta – Evolution • Share features with gymnosperms AND angiosperms – Gymno: seeds not enclosed in ovary – Angio: vessels in wood, somewhat flower-like structures, double fertilization • BUT some primitive angiosperms do not have vessels (e.g., Winteraceae) • Recent data suggest a … Reproductive structures are located in a flower. Anthocerotophyta is the least diverse phylum of the bryophytes, however its distribution is widespread, with Antarctica being the only continent in which they are not found. The fourth phylum (the Gnetophyta) are considered the closest group to angiosperms because they produce true xylem tissue. Simple microgametophytes and megagametophytes. Female Plant A female Ginkgo biloba produces seeds that are covered by an outer layer, sometimes referred to … However, these three phyla are not closely related phylogenetically to each other. The gnetophytes are reduced to three far-flung and remarkably different genera (each genus in its own order). The microgametophyte is a three‐nucleate structure, the megagametophyte an eight‐nucleate one. However, the similarities in reproductive structures serve to unite the taxa (see the description below). Maxfocus/iStock/Getty Images Plus. Gnetophyta are therefore said to be "gymnospermous." The Gnetophyta include only three genera Ephedra, Gnetum, and Welwitschia—each of which belongs to a … They have very few vegetative synapomorphies except decussate leaves. Gnetophyta seeds are said to be "naked" since they lack a particular sort of protective covering characteristic of Anthophyta. COMPARISON OF STRUCTURES IN GYMNOSPERMS Coniferophyta Cycadophyta Ginkgophyta Gnetophyta LEAVES Needle-like (small, long & narrow) Compound leaves (resembles palms or ferns) Fan-shaped leaves Broad leaves like angiosperms SEEDS Seeds in cones Seeds in cones Seeds are completely exposed Seeds in cones arranged in clusters … Stamens with two pairs of pollen sacs. The last phylum, Gnetophyta, is a diverse group of plants that produce vessel elements in their wood. The gnetophytes are a small group of vascular seed plants composing the phylum Gnetophyta, which is one of four phyla of gymnosperms that have living representatives. Gnetophytes, in the phylum Gnetophyta, are a very small and unusual group of plants. Ginkgo biloba is considered to be dioecious, or (possessing) male and female organs on different trees; because of this we will take a careful look at both the male and female plants. Gnetophyta is heterosporous and, in addition, produce highly specialized, complex reproductive and dispersal structures called seeds. INTRODUCTION TO THE GNETOPHYTA. Examples of conifers include pines, sequoias, firs, hemlock, and spruces. Gymnosperms: Cycad Cones. Conifers are the dominant phylum of gymnosperms, with the most variety of species. GNETOPHYTA- gymnosperm 1. Most species in this phylum typically grow on moist soil in shaded areas, but some are found growing in … Welwitschia produces extremely long leaves and is found in the deserts of southwestern Africa (Figure below). At what stage does the diploid zygote form? Reproduction. After fertilization, the ovary thickens and forms a fruit. The Coniferophyta division contains conifers, which have the greatest variety of species among gymnosperms.Most conifers are evergreen (retain their leaves throughout the year) and include some of the largest, tallest and oldest trees on the planet. Coniferophytes. 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