"When It Dries" was cut at some point during the run, and "Poppa Knows Best" was considerably shortened.
Different performance totals are given in different sources. The Best Plays of 1970-1971 lists a run of 351 performances, but Variety and Theatre World both reported 343. While most of the time we would be inclined to trust Variety and Theatre World over Best Plays, in this case Best Plays seems to be correct.
Some online sources report 6 previews, but that is incorrect. There were 14 previews, starting on October 28, 1970. There was originally to be only one Broadway preview, but the show opened extraordinarily long in New Haven — contemporary reports put the first performance at close to four hours — and much cutting and reworking was deemed necessary, especially after poor reviews greeted the Boston opening that followed New Haven.
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