When I started this I assumed that the quotation was by Groucho Marx and searched for an appropriate 16 word quote, without success. Since then I've solved all the clues (except 24) and made several more searches. Either I'm seeing, but not recognising the quote, or I'm searching in the wrong places.
I've never thought Groucho Marx funny and if I have to read one more of his witticisms I'lll be sick. Someone please put me out of my misery.
(The only searchable word I thought might be in the perimeter was 'smoke' but that was no help.)
Michael