DOWNWARD TRANSPORT THROUGH THE XYLEM 89 



been suggested by Pfeffer (1900, Vol. 1, p. 589) that the 

 bending movements of stems might aid in translocation, 

 she studied the effects of bending and twisting and other- 

 wise manipulating strips of phloem from Cornus alba and 

 Liguster amurense. The treatments, however, had no 

 tendency to hasten movement. Further attempts were 

 made to increase the movement by causing evaporation 

 from the exposed ends of the strips of phloem or paren- 

 chyma, the lower ends of which were dipping into the salt 

 solution, but here also there was no increase in rate of move- 

 ment over that in completely turgid tissues which were 

 kept well moistened. 



Experiments were also tried in which the phloem was 

 separated from the xylem for a distance of from 6 to 25 cm. 

 but with one or both ends left attached to the xylem. 

 "Plastilina" was placed between the xylem and the sepa- 

 rated phloem tissue so that cross transfer could not take 

 place. The phloem thus isolated was kept from drying by 

 encasing the entire stem in glass cylinders with moist filter 

 paper. Both cut branches and rooted plants were used, 

 but in all instances the lithium solution was introduced 

 through the cut end of the stem or a cut side branch. 

 Leaves were present both above and below the region where 

 the phloem was separated from the xylem. Though within 

 from three quarters of an hour to an hour, lithium had 

 moved through the xylem to the farthest tips of the plant 

 and quickly passed over into the phloem from the xylem, 

 the longitudinal movement through the phloem, where 

 it was separated from the xylem, was extremely slow. 

 After from 20 to 26 hr. the lithium had spread longitudi- 

 nally through the phloem either from above or below a 

 distance of only 1.5 to 5.0 cm. In one instance it seemed 

 to have moved 15 cm., but this she considered an exception 

 and marked it with a question mark. In comparable 

 experiments with several twigs in which the phloem was 

 connected at one end only, the lithium was found to have 

 moved through the phloem for distances of only 2.0 to 

 3.8 cm. in 40 to 50 hr. In rooted plants of Cornus alba 



