Sentence:  We have distinguished two types of situations from the point of view of the placement of the obligatory X constituent within the phrase XP: one in which X is a <WSD>daughter</WSD> of XP, and one in which X is not a <WSD>daughter</WSD> of XP, but a <WSD>daughter</WSD> of one of the constituents of XP (in an adjunct configuration). 
Meaning of the word marked with <WSD> tags:  A descendant.