. The causes and course of organic evolution; . c Fig, 3.—Young seedlings of pea. a, radicle when placed transversely hasresponded directly at its tip to gravity by bending downward; h, oblique posi-tion of tip due to hydrotropic action of moist sponge, sp, that has slightlycounteracted geotropic action; c, downward growth of tip, as due to geotropism,and hydrotropism from moisture in dish below, both slightly counteracted byapoheliotropic effect of light from slit s in belljar covered with black paper, hp. cent to the sponge will grow as in (b). The third grows nearlydownward in virtue of gra
. The causes and course of organic evolution; . c Fig, 3.—Young seedlings of pea. a, radicle when placed transversely hasresponded directly at its tip to gravity by bending downward; h, oblique posi-tion of tip due to hydrotropic action of moist sponge, sp, that has slightlycounteracted geotropic action; c, downward growth of tip, as due to geotropism,and hydrotropism from moisture in dish below, both slightly counteracted byapoheliotropic effect of light from slit s in belljar covered with black paper, hp. cent to the sponge will grow as in (b). The third grows nearlydownward in virtue of gravity acting powerfully in a straightline upward, and equally of moisture that rises upward. Butthe lumic stimulus is sufficiently powerful to cause the root tobend away from the light, and to a slight degree therefore tobend away from the downwardly vertical, that indicates theresponse to gravic and hydric stimulus. The second takes thecourse sho^\^l, because the hydrotactic stimulus of the wetsponge plus the negative lumic stimulus greatly
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