树干为什么是圆的卓秀云如果我们留心身边的世界。就会发现多看起来平平常常、司空见惯的事物，其实蕴含着很深的科学道理。就拿树木来说吧！无论高的、矮的、粗的、细的，它们的树干部是圆柱形的。花有色彩之分。树叶有形态之异，树干为什么没有其它形状呢？首先，一株纤... Why the trunk is round Zhuo Xiuyun If we pay attention to the world around us. You will find that many seemingly ordinary, commonplace things, in fact, contains a lot of scientific truth. Take trees for example! No matter tall, short, thick, thin, their trunks are cylindrical. Flowers have color points. Leaves have morphological differences, why the trunk does not have other shapes? First, a fiber ...