aphercotropism

— Aphercotropism.— “Turning away from an obstruction” is a peculiarity discovered by Darwin. His experiment was as follows:— after allowing a radicle to be well developed in peas, beans, &c, the seed is suspended in the air. A tiny piece of card is attached to one side of the tip by a little gum; the tip will now move away from the vertical position, on the opposite side to the card. The tip may make one or more complete circles in a vertical plane; and it has been known to pass through the first loop so as to tie itself into a knot.