Device for Measuring Entry of Water into Roots

1. A potometric device for the quantitative determination of water movement into roots is described. The apparatus is designed so that it may be attached to any part of the root. 2. Experiments with young roots of corn indicate that the rate of water entry increases from the zone proximal to the root cap to a maximum at a point 10 cm. from the root tip. In most cases the rate decreases above this level in roots more than 10 cm. in length. 3. The lateral entry of water into older portions of Citrus roots is measurable, and ``they probably provide the major avenue of ingress during certain seasons of the year. The root lenticels may be the structures through which water most readily enters older portions of the root.