As early as eighteen thirty-seven, he imagined this process as a tree with branches representing new species.

VOA: special.2009.02.25

She knew this because sometimes the moon got caught in the top of the tree.

VOA: special.2009.03.28

Strangely enough she discovered this in a different kind of tree.

VOA: special.2009.11.15

"You see the river is a tree line, and all this is basically fresh-water marsh."

VOA: standard.2010.05.09

Using samples from around Southeast Asia, Buckley and his colleagues saw this pattern in tree rings from recent years, when he could corroborate the rings with other historical climate information.

VOA: standard.2010.04.05