THE METHOD OF MOVEMENT 215 



movement in unit time) and the intensity (the amount of 

 substance in unit time) are independent of the length of 

 the coleoptile cyhnder used. If diffusion accounted for 

 movement, the intensity should be inversely proportional 

 to the length of the cylinder. This was actually demon- 

 strated to be the case when agar cylinders and not coleoptile 

 cylinders were used. (2) The movement of the growth 

 substance through the coleoptile is strictly polar, that is, it 

 is carried only in a basal direction. It follows from this 

 that, in equal times and with equal initial concentration 

 in the agar plates, equal amounts will be transported 

 through coleoptile cylinders to agar plates at the base 

 independently of whether, at the start, the basal plate 

 'had no growth substance or a concentration of growth 

 substance many times that in the upper plate from which 

 it is moving. (3) With increasing initial concentration of 

 growth substance the absolute transport intensity increases 

 while the relative intensity decreases (according to dif- 

 fusion the absolute transport intensity should be pro- 

 portional to the concentration). The velocity of transport 

 is independent of the initial concentration. (4) The 

 velocity of transport in the coleoptile seems almost com- 

 pletely independent of the temperature. Below 40 to 

 45°C. the influence of the temperature on transport 

 intensity displays an optimum curve comparable to that 

 of a hfe process. (5) While (2) and (3) apply for coleoptile 

 cylinders at 0°C. as well as at higher temperatures the 

 transport in cylinders of various lengths at 0°C. behaves 

 more according to a diffusion scheme, but the movement 

 is still polar at 0°C. and in this respect is unlike diffusion. 

 Van der Wey states that it is not possible from his inves- 

 tigations to form a definite idea as to the method of trans- 

 port. He says, however, that the evidence is clear that 

 normal transport is a vital process, that movement is 

 strictly polar, and that it is totally independent of pro- 

 toplasmic streaming. The strongest evidence for its 

 independence of protoplasmic streaming is that, if this 

 accounted for transport, both velocity and intensity 



