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.