11 



§2, Preliminary investigations on the influence 

 f te m p e r a t u r e on g e o t r o p i s m. 



The influence of température on geotropic phenomena 

 has been traced chiefly by Czapek and by Bach, whose 

 results however do not agrée in ail points. 



The earliest experiments of Czapek were publishod in 

 1895. With the purpose of investigating, whether perception 

 and reaction could be separated, roots of Vicia Faba and 

 Lupinus and hypocotyls of Helianthus were stimulated at 

 0° C, at which température growth and therefore reaction 

 is impossible. 



Perception appeared to be possible at 0° C. ; the presen- 

 tation-time at 0° C. amounted to about 18 hours according 

 to thèse experiments. In addition, comparative experiments 

 were made to détermine the time during which a stimu- 

 lation subsides at ordinary température and at 0° C. In 

 the last case the subsidence is much faster. 



A few years latèr Czapek traced the influence of tem- 

 pérature more fully; the figures obtained in this research 

 are to be found in his paper of the year 1898. 



The following table gives a summary of the results, 

 obtained with germinating roots of Lupinus albus. 



Lupinus albus, germinating roots. 

 Température. Presentation-time. Reaction-time. 



