In a flower 3 petals are free and two petals of  the flower are fused. Such flowers are seen in

In pea the corolla is of papilionaceous and shows vexillary aestivation. In such corolla, the two anterior petals are fused at their margin and called as keel or carina. The two lateral petals are free and have intermediate size. The larger odd petal of posterior side is the largest and attractive and free. In Cassia all five petals are free. In Calotropis the five petals are fused. In Cotton the five petals are free.