Read it through once

It is probably because of this perpetual warfare that the growth of the grasses is so vigorous, and their whole structure so perfectly adapted. If you watch a flowering grass, you are sure to notice how narrow is its stem compared with the height. A factory chimney only fifty-eight feet high requires to be at least four feet broad at the base, yet a ryeplant 1500 millimetres high may be only three millimetres broad near the root. Man's handiwork, the chimney, is in height seventeen times its diameter, but the height of the grass is 500 times its diameter.