Listen again to part of the lecture, then answer the question.
再听一遍这个演讲中的一小节，然后回答问题。
I read about this and the book said one thousand kilometers of roots.
我阅读过这个，书上说，根有一千千米长。
I kept thinking: this has to be a mistake.
我一直在想：这肯定是个错误。
It just doesn't make any sense to me that...that...that could be right.
我觉得没道理，那不是对的。
But that's what all the books have, and no one's ever corrected it. So, let me explain to you about this rye plant.
但是所有的书上都是那样写的，没有人修改过。那么，我来给你们解释下这株黑麦。
What does the professor intend to explain?
教授要解释什么？