206 TRANSLOCATION IN PLANTS 



ward only through the petiole to the stem from where it 

 moved upward only, downward only, or in both directions. 

 For the most part the movement was chiefly toward the 

 growing point, and during June and July it was exclusively 

 in that direction, but the dye never entered even the 

 youngest leaves. In some of the other species of plants 

 tested this polar movement was not so marked. 



The rate of movement was markedly influenced by 

 temperature. In a warm room at 30°C. the fluorescein 

 had passed through an entire petiole in one hour. Several 

 measurements indicated rates of from 30 to 35 cm. an 

 hour. In a cool room at 11 to 12°C. it required 3 to 4 

 hr. for detectable amounts to pass into the veins, while at 

 1 to 4°C. it took up to 10 hr. before movement into veins 

 could be detected. After this long period movement sud- 

 denly commenced and the dye was carried throughout the 

 plant but at a slow rate, only 1 to 3 cm. an hour. If first 

 placed in a warm room, the dye was quickly absorbed and 

 carried into the petiole, but if the plant was then placed 

 in a cold room, movement stopped. Therefore the delay 

 in movement in a cold room is not due to a failure to 

 enter the sieve tubes. 



The rate of movement of fluorescein seemed almost 

 completely uninfluenced by the narcotics, chloroform, 

 ether, phenylurethane, and ethylurethane, unless they 

 were at concentrations sufficiently high to cause death. 

 Furthermore, the movement appeared to be uninfluenced 

 by wilting, was insensitive to light, and seemed in no way 

 dependent upon the movement of carbohydrates or nitro- 

 gen compounds. In his earlier paper (1930) Schumacher 

 found that carbohydrate transport from the leaf became 

 clearly apparent after 2 to 3 hours in darkness. After 

 24 hr. in darkness both carbohydrate and nitrogen trans- 

 port from leaves were active, but after 3 days nitrogen 

 removal was complete. With fluorescein he found no 

 difference in rate of transport from leaves in light as 

 compared with that from leaves which had been in dark- 

 ness for from a few hours up to 7 days. 



