The cause of plagiotropy in maritime shore plants 19 



iniilus reactions and growth movements, and are not due to variations in turgoi', 

 will be given later. 



The varying positions which the branches take up according to the strength 

 of illumination is also demonstrated in the following tables (VlII and IX) where 

 the data on experiments carried out during the period V12 — Vis have been brought 

 together. The light intensity was measured at noon and at 3 o'clock p. m. every 

 day, and these values are placed under the dates in the tables. The angles were 

 measured at 5 p. m. hi the case of Sneda maritima the number of degrees has 

 reference to the angles formed by the branches with the perpendicular, for the 

 Atriplex-iovms the deviation from the horizon is measured. 



Table VIII. 1 Sueda maritima, 2 Ätriplex prostratum. 





Vl4 



7; 6,5 



9; 16 



7 ; 6 



Vit 

 8; 7 



V18 

 8; 6 



Final 

 position 



Deviation 





63 



+ 11 



— 17 



+ 0 



- 13 



82 



— 19 



I 



71, 56 



+ 37, + 8 



— 35, — 18 



-2, +3 



— 7, — 14 



77, 77 



- 6,-21 





53, 56 



+ 4, +25 



- 2,-11 



-8,-7 



— 5, —16 



64, 65 



— 11, - 9 



2 



27, 36 



— 21, -28 



-3,-4 



±0,-1 



±0, ± 0 



3, 3 



— 24, — 33 



Table IX. 1 and 2 Sueda maritima, 3 Atriplex BaMngtonii. 





Vu 



10; 15 



V» 



9; 11 



V" 



7; 6,5 



9; 16 



Vie 

 7; G 



Vl7 



8; 7 



Pinal 

 position 



Deviation 



1 



51, 50 

 53, 51 



-2+0 

 — 4 -2 



— 12 - 5 



— 12, — 4 



+ 15, +13 



+ 7. + 12 



— 2,— 5 



— 2,-14 



+ 2,- 6 

 - 1,-20 



50, 53 

 59, 79 



+ 1,-3 

 — 6, - 18 



2 



60, 48 

 55, 50 

 62 



+ 0, + 0 

 -2,-2 

 ± 0 



-2,-2 

 - 4, - 3 

 ± 0 



+ 5, + 6 

 + 5. + 9 

 + 6 



± 0, ± 0 

 ±0,-17 

 — 3 



+ 0,-3 

 -1,-7 

 — 8 



57, 47 

 57, 70 

 67 



+ 3, + 1 

 — 2,-20 

 — 5 



3 



80, 76 



-7,-7 



— 19, — 14 



+ 6, +13 



+ 0, — 3 



-1, ± 0 



59, 65 



— 21, — 11 



Sueda maritima shows an upward movement in both series of experiments on 

 July 15. The light intensity decreased on this day down to 16 on account of 

 cloudiness and the consequence was that growth now proceeded in the direction to- 

 wards the vertical position. That Atriplex prostratum in spite of the lesser illumina- 

 tion shows downward movements is due to the fact that this species is plagiotropic 

 already in rather weak hght in the same manner as other prostrate forms belonging 

 to this genus. A. Babifigtonii is intermediate with regard to the strength of hght 

 necessary to bring about an alteration in the reaction. These questions will be 

 discussed in greater detail later. 



It has already been pointed out that the curvatures in question are not caused 

 by variations in turgor but come about through growth. The evidence brought 



