Plant Kingdom

Gymnosperms are the most primitive seed plants. The plants are generally perennial, woody trees or shrubs. In general, tallest trees in gymnosperms, e.g., Sequoia sempervirens is 366 ft. in height. The male gametes of Cycas are largest (300 $\mu $) in size, they are visible to naked eye and are oval in form and top-shaped. The ovule of Cycas is also largest in the plant kingdom.

A fern plant body is sporophytic (2n) and is differentiated into roots, stems and leaves. On the ventral surface of leaves sporangia are borne in a group called sori. Inside the sporangium are present the spores which are formed by reduction division.

Thus the spores produced are haploid in nature and germinate to produce a prothallus that represents the gametophytic generation. Antheridium and archegonium are borne on this prothallus. Thus meiosis takes place at the stage of spore formation.