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Monsanto Co. (NYSE: MON) tried for four years to acquire Germany-based Syngenta A.G. (NYSE: SYT), before finally giving up in February when China National Chemical (ChemChina) offered around $46 billion for the pesticide maker. Now, another Germany-based agricultural giant, Bayer, is offering to buy Monsanto.

Few details are available, although Monsanto did acknowledge late Wednesday that it has received “an unsolicited, non-binding proposal from Bayer AG for a potential acquisition of Monsanto, subject to due diligence, regulatory approvals and other conditions.”

At Wednesday’s closing share price of $97.13, Monsanto’s market cap is $42.43 billion, so any offer from Bayer would likely be north of that number.

Consolidation in the seed and pesticide business is forcing Bayer’s hand, just as Monsanto felt it had to do its best to acquire Syngenta. The coming merger of Dow Chemical Co. (NYSE: DOW) and E.I. du Pont de Nemours and Co. (NYSE: DD) and the Syngenta-ChemChina deal create bigger rivals that may gain a competitive advantage due to their scale.

Bayer is currently the world’s largest firm in the seed and pesticide business with a market cap of around $74 billion. Another German firm, BASF, is second at around $61 billion, followed by Dow, DuPont, Monsanto and Syngenta. Monsanto is the world leader in seed sales, primarily on the strength of its North American markets. Bayer’s primary seed markets are located in Europe and Asia.

Monsanto’s shares traded up almost 5% to $101.89 late Thursday morning, in a 52-week range of $81.22 to $121.09.