Mass Extinctions Rise Among Plant Species

Entire species of plants are dying off in droves, just like mammals. And there's no way to save them all, say scientists. How do you decide which plant species to preserve at all costs, and which ones to consign to oblivion forever? Answering that question may mean the difference between selective extinction for some… » 10/22/08 8:40am 10/22/08 8:40am