This clade underwent significant radiation in the middle Cretaceous, displacing the more basal Cycad
This clade underwent significant radiation in the middle Cretaceous, displacing the more basal Cycadophyta. When certain parts of their perianths are undifferentiated from one another, those structures are termed tepals. Members of this clade develop a nutritive tissue around the embryo from one sperm nucleus and two polar bodies after another cell forms a tube down the style; that process is called double fertilization. Traditionally divided into monocots and dicots, these plants possesses reproductive organs called pistils and stamens and often have colorful petals. For 10 points, identify this division of seed-bearing flowering plants, a sister clade to Gymnospermae. 
This clade underwent significant radiation in the middle Cretaceous, displacing the more basal Cycadophyta.
angiosperms [or Angiospermae; or Magnoliophyta; or magnoliophytes; or Anthophyta; or anthophytes; accept flowering plants until it is read; prompt on "flowers"] 