16 TRANSLOCATION IN PLANTS 



regions corresponding to above, between, and below the 

 rings. No starch was present in the xylem rays or cortex. 

 The period from May 5 to 19 was favorable for rapid growth 

 and utilization of the stored foods as the rainfall preceding 

 and during this period was considerably above the normal ; 

 the temperature also was high and the days were cloudy, 

 tending to interfere with the manufacture of carbohydrate 

 by the young leaves. The part above the upper ring was 

 therefore quickly depleted of its stored carbohydrates by 

 the many growing shoots. The part between the rings 

 bore no shoots and seemed to have lost none of its starch, 

 while the part below the lower ring, though it bore no 

 shoots, had become almost depleted of starch. Evidently 

 the sugars from this part had moved back to the fork 

 from where they had been carried either up to the growing 

 shoots of the unringed arm or back to some other part of the 

 tree. 



Similar results from experiments on double-ringing were 

 repeatedly obtained with all the plants tested, which, in 

 addition to Ostrya included Acer saccharum, Fagus grandi- 

 folia, pear, apple, and several species of Crataegus. A 

 total of several hundred stems were thus double-ringed. 

 In all cases, when the starch had completely or almost 

 completely disappeared from the parts above the upper 

 ring and had largely disappeared below the lower ring, 

 that part between the rings and isolated by them from the 

 food-consuming tissues contained an abundance of starch. 



The rapidity and completeness of the starch removal 

 above the upper ring are evidently determined by several 

 conditions. If the upper ring is made close to the terminal 

 bud, the amount of food stored above it is small and the 

 depletion will be more rapid and more complete, while if 

 the ring is made on an older stem, the depletion is less 

 rapid and less complete (see Table 1). The environment 

 also influences the rate and amount of removal. If the 

 water supply is plentiful and the temperature high, growth 

 will be rapid and the carbohydrates more rapidly depleted. 

 If also the light intensity is low, the reformation of car- 



