After the ball was over and the taxi-cab was underway some one suggested midnight chow, permitted by the censor.

In order to account for this, we might propose to make the Prepositional Phrase an optional constituent of the Verb Phrase: this we could do by re- placing rule (28) (ii) by rule (40) below: (40) VP → V AP (PP) (Note that a constituent in parentheses is, by convention, taken to be optional.)

Of course the rolling stock is furnished in a style as modern as tomorrow, with a complete absence of dust traps and fussiness.

All ingress was prohibited.