<prompt> Marking nut isSemicarpus anacardiumCroton tigliumAreca catechuAbrus precatorius  <response>: Ans. is a i.e., Semicarpus anacardium Semicarpus anacardium marking nut or bhilawan Its seed are heart shaped, conical and black with acrid oily juice which is brownish but turns black on exposure to air. Active principles are semecarpol and bhilawanol. Juice applied to skin produces irritation, painful blisters followed by itching and eczema. Therefore it is used to produce artificial bruises. It is also used by washerman to mark clothes. 