CHAPTER II. 



Material. General arrangement of the 

 Experiments. 



Material. 



Seedlings of Avena sativa were chosen as expérimental 

 objects, because numerous recentinvestigations hâve shown 

 them to be a very suitable material for geotropic and 

 phototropic experiments, and further seedlings of Sinapis 

 alba, for reasons which will be given later. The oat- 

 grains were peeled before use. For the rest the seeds were 

 treated alike, i. c. they were first placed on damp fîlter- 

 paper to germinate and later transplanted into boxes with 

 soi!. This method is described in detailed by Rutgers^). 

 The oat-grains had to lie for 2 days on the fîlter-paper 

 and had then germinated sufficiently to be planted. This 

 time varied somewhat for the seeds of Sinapis being 

 between four and six days. The culture-boxes were of 

 zinc, and measured 10 X 3 X 3 cm. Nine seeds were 

 planted in each vessel. They were placed diagonally for 

 the photropic experiments in order to avoid mutual 

 shading when illuminated. The oats were of one pure 

 strain "Svalôfs Goldregnshavre". The seeds of Sinapis 

 were ordinary commercial seeds. Very many of them 



') A. A. L. Rutgers. De invloed der temperatuur op den praesen- 

 tatietijd bij de geotropie. Dissertatie 1910, p. 41. 



