CHAPTER I. 

 Review of the Literature. 



The fîrst investigations on the question whether free 

 oxygen is necessary for the appearance of a phototropic cur- 

 vature, date from Payer ^). He worked with seedhngs of 

 Lepidium sativum, and found, that the médium in which 

 the experiments were carried out, cannot inhibit a reaction, 

 but can diminish the curvature. Thus he saw very distinct 

 curvatures occur under water, and further in an atmos- 

 phère of nitrogen or hydrogen. 



Von Mohl~) accepted the accuracy of Payer's 

 investigations. He himself carried out no experiments in 

 this direction, but only used Payer's results in order to 

 controvert Dutrochet's ^) theory of Hght on a certain point. 



In 1878 the question of the dependence of heUotropic 

 processes on the présence of free oxygen was taken up 

 again by Wiesner*). He worked with seedhngs of 



^) T. Payer. Mémoire sur la tendance des tiges vers la lumière. 

 Comptes rendus 1842. T. XV, p. 1194. 



^) H. von Mohl. Grundziige der Anatomie und Physiologie der 

 vegetabilischen Zelle (Abdruck aus R. Wagner's Handwôrterbuch der 

 Physiologie 1851, p. 297). 



^) M. Dutrochet. Rapport sur un mémoire de M. Payer, intitulé 

 Mémoire sur la tendance des racines a fuir la lumière. Annales des 

 sciences naturelles, 1844, 3e série, T. II, p. 96. 



^) T. Wiesncr. Die heliotropischcn Erscheinungen im Pflanzenreiche, 

 eine physiologische Monographie 1878, p. 58. 



Receuil des trav. bot. Néerl. Vol. XIII. 1916. 11 



