in a tree和on a tree的区别

　　The path led through the trees to the river.

　　这条小路穿过树林通向河边。

　　They cut away all the dead branches from the tree.

　　他们把这棵树上的枯枝全都砍掉了。

　　The house is easily identifiable by the large tree outside.

　　这房子很容易从外面的这棵大树辨认出来。