Top­shaped multiciliate male gametes and the mature seed which bears only one embryo with two cotyledons, are characterised features of

Explanation

a. Cycas is an evergreen palm-like plant. The plant body is sporophytic differentiated into root, stem, and leaves, sexual reproduction is of oogamous type takes place by the fusion of distinct male and female gametes. The male and female gametes are formed by the germination of microspores and megaspores which are borne on microsporophylls and megasporophylls. These microspores germinate to form a male gametophyte that produces male gametes. The male gametes of Cycas are the largest (300 m) in nature, visible to the naked eye, oval in form, and top-shaped. It is spirally coiled in the anterior half with thousands of small cilia. After fertilization, the ovule is connected to a seed. In the endosperm of seed lies a well-developed embryo having two cotyledons, a plumule, and a radicle.Cycads are gymnosperms characterized by having top-shaped multiciliate male gametes. These male gametes have many hair-like projections, which aid in fertilization. Additionally, cycads typically produce seeds with a single embryo and multiple cotyledons. b.Conifers, on the other hand, usually have seeds with a single embryo and two cotyledons, and their male gametes are not multiciliate. Conifers do not have top-shaped multiciliate male gametes. They produce male gametes in the form of pollen grains containing non-ciliate sperm cells. c. This term refers to angiosperms (flowering plants) with separate or distinct petals on their flowers. Angiosperms typically have seeds with two cotyledons, but they do not produce top-shaped multiciliate male gametes. d. This term refers to angiosperms with fused petals. Angiosperms usually have seeds with two cotyledons, but they do not produce top-shaped multiciliate male gametes.