Note 9a — Chapter I · Twining Plants.

This whole subject has been ably discussed and explained by H. de Vries, ‘Arbeiten des Bot. Instituts in Würzburg,’ Heft iii. pp. 331, 336. See also Sachs (‘Text-Book of Botany,’ English translation, 1875, p. 770), who concludes “that torsion is the result of growth continuing in the outer layers after it has ceased or begun to cease in the inner layers.”