Question
Biology Question on Angiosperms
Gnetum is considered closer to angiosperms than Cycas and Pinus because of
presence of perianth and two integuments
post fertilization development of endosperm
absence of resin duct and leaf venation
presence of vessel elements and absence of archegonia
presence of vessel elements and absence of archegonia
Solution
Unlike Cycas and Pinus and most other gymnosperms Gnetum shows the occurrence of vessel elements and the absence of archegonia. Archegonia are altogether absent in the female gametophyte and vessels occur in the xylem along with the tracheids in the secondary wood. Thus, Gnetum shows affinities with angiosperms. Besides, it resembles angiosperms in several other aspects like free nuclear divisions in the embryo sac, two cotyledonous embryo, etc.