20 



Göte Tuiessoti 



forth in tables VI and VII favours this belief. The results of an investigation of 

 the resistance to flexion of the lateral branches of Atriplex prostratum Bouch (tabulated 

 in table X) also argue in the favour of this opinion. Four cultures were experi- 

 mented on and two branches on each, one long(l), and one short (2) were observed. 

 After measuring the angle (a) between the branch and the chief axis, the plant was 



turned through an angle of 180° until the 

 branch was again horizontal and tlie angle (a^) 

 was once more measured. The difference be- 

 tween these two angles (a— a^) affords an esti- 

 mate of the resistance to flexion (Jost 8). When 

 exposed to light for two hours a value of 4 — 9 

 was found for the short branches and a value 

 of 12 — 22 for the long ones. In darkness 

 during the same length of time the value for 

 the short branches was found to be 8—11, for 

 the long ones 15 — 26. An increase in the 

 resistance to flexion is thus seen to take place 

 when the plants are illuminated. Other experi- 

 ments to be mentioned in the following are conclusive and show with the greatest 

 clearness that the movements which lead to the plagiotropic orientation of the bran- 

 ches are due to growth. 



Cultures of Atriplex prostratum Bouch. grown in different concentrations of 

 sodium chloride showed that growth reaches its maximum in a 1 7o NaCl solution. 

 Growth is considerably retarded in a 1,6 "/o solution and is very slow in 2 7o so- 

 lutions. Further details will be given on anotlier occasion. However, cultures watered 

 for some time with fresh water and solutions of 0,26 7^ NaCl; 0,5 7» NaCl; 1,6 7o 

 NaCl and 2 °/o NaCl were used in studying the plagiotropy, and the results ob- 

 tained will be given here. The different cultures were exposed to direct sunlight 

 having an intensity amounting to 6 — 8 during 6 hours, and were then put in the 

 dark room and measured again after 24 hours. The angles formed by the lateral 

 branches with the perpendicular are tabulated in table XI (light) and in table XII 

 (darkness). It may be added that the plants used in these experiments were of 

 the same age and genetically pure. The numerals in the last column indicate the 

 mean value of the deviations of the branches. 



Light 

 Diff. between a — aj 



Darkness 

 Diff. betw. a — 



1 



1 



12 



15 



2 



7 



11 



2 



1 



22 



26 





2 



4 



4 



3 



1 



11 



18 





2 



8 



8 



4 



1 



14 



15 



2 



9 



10 



