猴子在树上用in不用on。in the tree是指不是树上生长的东西到了树上，常用于修饰藏于树中的动物或人；on the tree是指树上生长出来的东西，常用于修饰树上的果实、叶子等。
一、on the tree的含义及用法
on the tree意为在树上，是指树上生长出来的东西。例句有：
1、She bumped her arm on the tree.
她的手臂撞到了树上。
2、We followed the marks he had made on the tree trunks.
我们按他在树干上做的记号往前走。
3、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。
4、Would you like to put the star on the tree?
你能把这颗星星放在圣诞树上吗？
5、You guys are a little early on the tree though.
你家现在就放棵树是不是太早了。
二、in the tree的含义及用法
in the tree意为在树上，是指不是树上生长的东西到了树上。例句有：
1、The boys carved their names in the tree.
男孩子们把名字刻在树上。
2、A little bird was singing happily in the tree.
小鸟在树上快乐地歌唱。
3、One day, a bird came and nested in the tree.
一天,一只鸟来了,在树上筑巢。
4、The artist painted a green and yellow leaf, then put it in the tree.
画家画了一片绿黄相间的叶子,然后把它放在树上。
5、There is not in the valley a tree or a stone I don't know.
这山谷里的一草一木我无不熟悉。
