Horizontally growing root tips from red maple trees (Acer rubrum L.), when grown through a holder and then deflected laterally by a barrier, curve back toward their original direction as they grow beyond the barrier. The amount of recurvature increases as the angle of the barrier is increased up to a barrier angle of 60[degree] but decreases only slightly as barrier length is increased from 1 to 7 cm. The stimulus to recurve beyond the barrier appears to be the initial physical bending that produces asymmetry both in the root tip and in the bent portion. Comparable behavior of horizontal root tips under natural conditions tends to produce long, straight roots radiating from the stem.