Missing apostrophes, misplaced apostrophes, and unnecessary apostrophes are all common occurrences in many forms of written American English. The fact is there is no adequate explanation--in traditional grammar or in any other grammar--that accounts for all the functions and transformations that grammarians have crowded under the heading of the genitive case. In fact, many writers who omit the possessive apostrophe, including freshmen writing students, do so quite logically, according to a set of "rules" not found in any grammar book. The most basic rule is as follows: when a noun phrase cannot be paraphrased as an unambiguous "possessive" using an "of" construction, writers tend to omit the apostrophe. One of the contingencies that complicates this rule is the issue of how"possession" is determined, as well as who/what is able to "possess." In other words, humans are considered more able than inanimate objects to "possess" a given object. In the end what is inarguable is that the phenomenon of the missing apostrophe in contemporary written English offers a unique opportunity to record and describe the kind of pervasive morphemic, grammatical and syntactical change that, for the most part, has only been observed in a post facto, static way. (TB)