长在树上用on the tree还是in the tree

on the tree指长在树上的东西 in the tree指树以外的东西；

比如apples on the tree, birds in the tree；

tree

n. 树;树木;乔木；

vt. 把…赶上树;使处于困境;把鞋型插入（鞋内）

Most of the apples on the tree have ripened.

树上的苹果大多已经成熟。

Day after day, there were less and less leaves on the tree.

日复一日,树上的叶子越来越少。

His speciality was psychology--one important branch on the great tree of knowledge.

他的专业是心理学，这是知识之树上的一个重要分枝。

The woodpecker pecked a hole in the tree.

啄木鸟在树上啄了一个洞。

There is a bird sitting in the tree.

树上卧着一只鸟。

A little bird was singing happily in the tree.

小鸟在树上快乐地歌唱。