The virgin forest with its richness and variety of trees was a real treasure-house which extended from Maine all the way down to Georgia.

原始森林树木郁郁葱葱、种类繁多，是一座真正的宝库，从缅因州向南一直延伸至乔治亚州。

It's just a map showing the diversity of tree species within the U. S., where the line is once again pretty clearly visible with significantly less variety of tree species to the west of it.

这只是一张显示美国境内树种多样性的地图，这条线再次清晰可见，它西边的树种多样性明显要少得多。