18. Answer very briefly IV

Gymnosperm are closed seeded plant.naked seed plant, because ovule is not enclosed by ovary.ovule is enclosed by ovary.. Gametophytic and Sporophytic are the two stages of a Gymnosperm's life cycle. The sporophytic generation is the recessivedominant  one that contains the reduced gametophytes. The sporophytic plant body is not differentiateddifferentiated into root, stem and leaf. They have undevelopedwell developed  vascular tissues. In these plants, water is conducted by the  sieve celltracheidsof the xylem, and food is conducted by the sieve cell of the phloem.