Which one of the following may require pollinators,but is genetically similar to autogamy?

Statement $(X)$: Endosperm is formed before fertilization.
Statement $(Y)$: Double fertilization is observed.

Identify the plant parts that consist of two generations,one within the other:
$(a)$ Pollen grains inside the anther
$(b)$ Germinated pollen grain with two male gametes
$(c)$ Seed inside the fruit
$(d)$ Embryo sac inside the ovule

If the root of a flowering plant has $24$ chromosomes,then how many chromosomes does its gamete have?

Who worked on embryological aspects and popularized the use of embryological characters in taxonomy?

All of the following are features of angiosperms except $-$