The part of the tree that's underground, way down there underground, is called the roots.

树的地下部分，在地下深处，被称为根。

Every company needs underground ways of poking fun at the organisation, says Lynn Mark, a speaker on workplace humour for St. Mary's Health Centre in St. Louis.

位于圣路易斯的圣玛丽健康中心的职场幽默演讲家琳恩·马克表示，每个公司都需要用秘密方式来自我娱乐。