bild

Roots of the annual meadow-grass, Poa annua. The pictures shows the roots of grass that has grown in the confined space of a seed tray. Unable to penetrate widely into natural soil, the roots have grown in parallel clusters resembling a cable network. The roots show a striking lack of lateral root formation under these conditions. (KEYSTONE/SCIENCE PHOTO LIBRARY/DR JEREMY BURGESS/SCIENCE PHOTO LIBRARY)