The roots are laid out on a flat surface, and a count is made of the number of intersections between the roots and random straight lines. Then the total root length = πNA/2H, where N is the number of intersections, A the area within which the roots lie, and H the total length of the straight lines. Details are given of a technique in which a microscope hair-line provides the straight lines. In practical tests the method was compared with direct measurement, and with direct measurement of a sub-sample followed by weighing of the sub-sample and the remainder. The results from the different methods agreed well. The line intersection method was much quicker than direct measurement, and in a given time achieved higher precision than measurement of a sub-sample and weighing.

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