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Each of these four categories has an auxiliary tree that is used for conjunction of two constituents of that category. The auxiliary tree adjoins into the left-hand-side component, and the right-hand-side component substitutes into the auxiliary tree.

 0.5in (a) 0.5in (b)

{Tree for adjective conjunction: $\beta$a1CONJa2 and a resulting parse tree

Figure 22.1(a) shows the auxiliary tree for adjective conjunction, and is used, for example, in the derivation of the parse tree for the noun phrase the dark and dreary day, as shown in Figure 22.1(b). The auxiliary tree adjoins onto the node for the left adjective, and the right adjective substitutes into the right hand side node of the auxiliary tree. The analysis for adverb, preposition and PP conjunction is exactly the same and there is a corresponding auxiliary tree for each of these that is identical to that of Figure 22.1(a) except, of course, for the node labels.

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