Trillium "erectum"

Do tell me why Trillium erectum is called that.

It's in no way erect - it's nodding. See for yourself:

Trillium erectum, red flower.Pic: Trillium erectum, red flower.

Trillium erectum, white flower.Pic: Trillium erectum, white flower.

And what's with the white and/or red flowers of Trilliums?

There's loads of trilliums

There's loads of trilliums (I've pics of 8 species now), and a few of them are white and pink or red.
Pollination, eh? Thanks for that!