Farm-fresh infringement: Can you violate a patent by planting some seeds?

In 1994, the agricultural giant Monsanto obtained a patent covering a line of "Roundup Ready" crops that had been genetically modified to resist Monsanto's Roundup herbicide. This genetic modification is hereditary, so future generations of seeds are also "Roundup Ready." Farmers had only to save a portion of their crop for re-planting the next season, and they wouldn't need to purchase new seed from Monsanto every year.

But Monsanto countered that each new generation of seeds is a separate product and thus requires a separate patent license. In effect, Monsanto contends that Bowman is illegally "manufacturing" infringing soybeans.