(FORTUNE Magazine) – The French stock market crashes. Traders rush to unload pounds and lire. The deutsche mark soars. Amid the frenzy, Europe's leaders scramble to control the crisis, realigning their currencies. They fail. The European Monetary System unravels, investment plunges, and a full-scale depression envelops the Continent. That's the catastrophic scenario painted by proponents of Europe's Maastricht Treaty if French voters kill the agreement for closer economic and political union in their September 20 referendum. According to the polls, the race is too close to call. Like President Francois Mitterrand, most French business leaders support Maastricht and have launched an unprecedented campaign for a oui vote. Realistically, a French no vote is unlikely to derail Europe's long march toward economic unity any more than the rejection of the treaty by Danish voters did earlier this year. All the progress made in breaking down the trade barriers in Europe would survive, and a single market would still go into effect as scheduled next January 1.

Still, most businessmen are wary. Without the single currency envisioned in the treaty, Europe will not have a truly free market. Even a narrow yes vote could prolong debate in Germany and Britain, whose parliaments have yet to approve the pact. French publishers are already prospering from the proposed treaty. More than a dozen books arguing Maastricht's pros and cons have appeared in recent weeks. The best-seller: Maastricht -- Mode D'emploi (user's guide) takes no sides. Instead, the $13, 628-page book reprints the treaty for 195 pages and devotes the remaining space to the Treaty of Rome, the original 1957 Common Market pact, and explanations of what all the international legalese really says. -- William Echikson

. . . OFFER $30 HOTELS With the dollar's drop, prices for some hotel rooms in France are astronomical. Paris's Ritz Hotel charges up to $1,000 a night, and even basic accommodation at Euro Disney runs more than $200. How can a U.S. visitor survive? One answer: Check in at Formule 1, a French chain with rooms that cost only $30 a night -- for one, two, or three occupants. But don't count on a helpful concierge. Guests check in with a credit card and may never meet a motel employee. The no-frills chain, owned by Groupe Accor, the giant French hotel company that also runs Motel 6 in the U.S., is among the fastest-growing in Europe. Started only in 1985, Formule now has 230 hotels in France and is expanding into Belgium, Britain, Germany, and the Netherlands. Formule 1 isn't popular just among budget-conscious tourists, either. Jean- Francois Bourgois, head of the chain, says, ''More than two-thirds of our clients are businessmen.'' Among the regulars (see photo): Jean-Robert Leconte, who teaches driving courses at various locations. He uses the hotels four nights a week. Bourgois says he has no plans to take the Formule 1 formula across the Atlantic. He believes Americans will not accept sharing toilets and showers, or the small size of Formule 1 rooms, which measure 30 square feet, vs. an average 70 in the U.S. Formule hotels seem ripe for an amorous tryst. Au contraire, says Jean- Michel Billand, manager of a Formule 1 at Noisy-le-Grand near Euro Disney: ''It wouldn't be flattering to bring a mistress to a Formule. I would advise the Hilton for something like that.'' -- W.E.

. . . & NIX NUPTUALS Bishops have banned their priests from remarrying visiting Japanese honeymooners. This ends a five-year, TV-show-inspired fad that brought some 20,000 couples to France for both a religious ceremony and a civic blessing by a Tricolor-toting mayor. Price: $10,000 per couple for a ten-day visit plus $160 for the church and $200 for the town. Mayor Charles Fevre of Arc-en-Barrios in central France, who has blessed several such newlyweds, says it helps Franco-Japanese detente. The bishops say it's a sham since most of the couples first wed as Shintos or Buddhists. Some priests refused to participate even before the ban. Says one, Rene Levresse of Strasbourg: ''The priest who does this turns himself into a comedian. This is not real marriage, it is cinema!'' -- A.McC.