Practice question

Although flower and fruit traditionally considered hallmarks, homoplasious structures exist: Gnetum produces bisexual strobili resembling flower with perianth-like bracts, some gymnosperm seeds develop fleshy sarcotesta mimicking fruit, vessel elements evolved convergently in Gnetales and angiosperms. Most unambiguous embryological evidence remains double fertilization producing embryo plus triploid endosperm via triple fusion, observed in all Angiospermae after careful microscopy requiring clearing techniques. Trait couples nutritive tissue formation to fertilization event, economizing resources and enabling imprinting parental conflict. Enclosed carpel forming ovary complements but fertilization biology provides mechanistic, phylogenetically conserved criterion separating flowering plants from gymnosperms in modern systematics.