Wasow (1977) argues that linguistic theory should recognize two qualitatively distinct types of rules: syntactic rules, which can affect more "superficial" grammatical function properties; and lexical rules, which affect deeper lexical semantic properties of lexical items. However, lexicalist theories of grammar have replaced syntactic rules with lexical rules leaving Wasow's dichotomy potentially unexplained. Our goal in this paper is to recapture Wasow's insight within a lexicalist framework such as HPSG. Building on Sag & Wasow's (1999) distinction between lexeme and word, we claim that there is a contrast between lexical rules that relate lexemes to lexemes (L-to-L rules) and lexical rules that relate words to words (W-to-W rules) and that these differences follow from the architecture of the grammar. In particular, we argue that syntactic function features (ARGST, VALENCE, etc.) are not defined for lexemes, while lexical semantic features (CONTENT) are. From this it follows that L-to-L rules can affect lexical semantic features, and not syntactic function features. In addition, since words are defined for syntactic function features, W-to-W rules can change them. In this paper, we support this hypothesis by examining certain differences between two types of Noun Incorporation construction, and their relation to other rules in the grammar. We argue that Compounding Noun Incorporation is an L-to-L type and that Classifier Noun Incorporation is a W-to-W type; we base our argument on the interaction of Noun Incorporation and Applicative Formation in the Paleo-Siberian language Chukchi and the isolate language Ainu.