When the margins of sepals or petals overlap one another without any particular direction, the condition is termed as Valvate, Imbricate, Twisted, or Vexillary?

The arrangement of sepals and petals of the flowers is referred to as aestivation. When the margins of petals overlap each other in such a way that one petal is completely external, one petal is completely internal it is called as imbricate aestivation as in Cassia and Bauhinia. Therefore, the correct answer is Imbricate.