The cause of plagiotrop}' in inaritinu' nhore plants 21 



Table Xr. 







Origin;\l 

 position 



Aflci- 6 lioai's 

 of illnmiii. 



Doviiilioii 



jVIgmU V'illuG 



1 



b'resh water 



32 

 (JO, 4« 



37 

 69, 50 



5 



— 9,-4 



— 6 



2 



0,-25°/o NaCl 



18, 29 

 2, 27 



18, 33 

 2, 32 



±0,-4 

 + 0,-5 



— 2,7 



3 



0,50 "/o NaCl 



2, 8 

 22, 30 



40, 20 

 33, 38 



— 38, — 12 



— 11, —8 



— 17,25 



4 



1,5 »/o NaCl 



36, 22 

 15, 17 



4i, 30 

 22, 28 



— 5,-8 



— 7, — 11 



— 7,75 



5 



2 "/o NaCl 



55 

 30, 38 



60 

 34, 45 



— 5 

 — 4,-7 



— 5,83 



Table XII. 







Oiiginal 

 position 



After 24 hours 

 of darkness 



Deviation 



Mean value 



1 



Fiesh water 



37 

 69, 50 



35 

 59, 37 



+ 2 

 + 10, +13 



+ 8,33 



2 



0,25 7o NaCl 



18, 33 

 2, 32 



18, 27 

 2, 26 



+ 0, +6 

 ±0, +6 



+ 3 



3 



0,50 7o NaCl 



40, 20 

 33, 38 



23, 7 

 27, 20 



+ 17, + 13 

 +6, + 18 



+ 13,5 



4 



1,5 7o NaCl 



41, 30 

 22, 28 



26, 16 

 22, 21 



+ 15, + 14 



+ 0, +7 



+ 9 



5 



2 0/0 NaCl 



60 

 34, 45 



45 

 33, 44 



+ 15 



+ 1, +1 



+ 5,67 



That the movements which these cultures execute in response to the conditions 

 of illumination are true growth movements is at once seen. The relation of the 

 concentration of the NaCl solutions to the rate of growth has already been men- 

 tioned. In these series the culture holding 0,5 °/o NaCl allows the most vigorous 

 growth; it shows also the greatest angular movements. The more vigorous the 

 growth the more rapid the movements. 



Before going any further in the analysis of the physiological nature of these 

 movements some experiments with Prunus spinosa and Coloneaster integerrima may 

 be discussed. These species are known to occur in espalier-shaped forms along ex- 

 posed coasts, and the opinion is often expressed that the strong wind is the direct 

 cause of the prostrate growth. However, Warming (31) has claimed that this factor 

 in not able to explain all the cases of prostrate growth observed by him in Primus 

 spinosa. Table XIII shows the result of 18 different trials with Primus twigs. Some 



