I see that the other plant discussion is closed; just as well. I resisted jumping in there--the Ur environment that was represented in sing-song is a way over-simplified goal. And, were it still open, I probably would have jumped in at the end to introduce the argument that some ethnographers and historians make, that the huge hardwood forest that Janie mentioned was also "artificial." By the time pioneers were hacking their way through that part of the continent a couple of hundred years after sustained contact with North America began, the theory is that millions of the Ur Indians on the continent had been killed off by introduced Euro diseases. Their cultivation and burning practices had gone away a couple of hundred years earlier after the disease vectors had done their work, allowing the forest to flourish as never before. (See Keepers of the Game by Calvin Martin).

SRS