桦树有白色的树皮，树上这个坚硬的保护外层，这个白色的树皮，是防水的。
The birch tree has white bark, and this tough protective outer layer of the tree, this white bark, is waterproof.
屋后的花园里有一大堆树皮，你必须站在那上面等着我。
In the garden behind the house is a large tan-heap, and on that you must stand and watch for me.
汞通过韧皮部被转运到树皮中，有选择性地在其中沉积，而非在自己不易更新的部位沉积。
Mercury is carried there by the phloem and selectively deposited in it, rather than in the plants' more permanent parts.
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