ABSTRACT
This chapter suspects that the apex was sensitive to contact, and that an effect was transmitted from it to the upper part of the radicle, which was thus excited to bend away from the touching object. Manner in which radicle's bend when they encounter an obstacle in the soil Vicia faba, tips of radicles highly sensitive to contact and other irritants effects of too high a temperature power of discriminating between objects attached on opposite sides. The circumnutating movement of the terminal growing part both of the primary and secondary radicles is so feeble that it can aid them very little in penetrating the ground, excepting when the superficial layer is very soft and damp. The chapter concludes that the initial power of an irritant on the apex of the radicle of the beam, is less than that of geotropism when acting at right angles, but greater than that of geotropism when acting obliquely on it.
