On the bases of several structural features, we can divide angiosperms into tow groups, called monocots and dicots. The names monocot and dicot refer to the first leaves that appear on the plant embryo. These embryonic leaves are called seed leaves or cotelydons. A monocot embryo has one seed leaf; a dicot embryo has two seed leaves. The flowers of most monocots have their petals and other parts in multiples of three. The dicot flower usually has petals and other parts in multiples of four or five. In the image below there is a group of dicots with five petals.