40 MOVEMENTS OF SEEDLINGS. 



Darwin tried many experiments to ascertain 

 how the movements of the radicle were affected 

 by contact with external objects. Some of these 

 experiments consisted in affixing, by shellac, or 

 gum, small bits of card to one side of the tip of 

 the radicle. The whole growing part of the radi- 

 cle bent away from the side bearing the card, or, 

 when card was placed on one side and paper on 

 the other, the radicle bent towards the thinner 

 paper. He also found that radicles bent toward 

 moisture and away from light. " It is not prob- 

 able that the tip when buried in compact earth 

 can actually circumnutate, and thus aid its down- 

 ward passage, but the circumnutating movement 

 will facilitate the tip entering any lateral or 

 oblique fissure in the earth, or a burrow made by 

 an earthworm or larva ; and it is certain that 

 roots often run down the old burrows of worms. 

 The tip, however, in endeavoring to circumnutate, 

 will continually press against the earth on all 

 sides, and this can hardly fail to be of the highest 



manner by the development of seedlings in crevices. Thus, at the 

 Marien Cemetery, in Hanover, Germany, the base of a tree has dislodged 

 the stones of a strongly built tomb. One of the stones, which measures 

 23 by 28 by 56 inches has been lifted upon one side to the height of five 

 inches. The tree measures just above its base from ten to fourteen inches 

 in diameter." "Physiological Botany." By George Lincoln Goodale. 

 Ivison, Blakeman, Taylor & Co. : New York and Chicago, p. 395, note 3. 



