UPWARD TRANSPORT OF ORGANIC MATTER 41 



experiment because the bushes were growing close to the 

 north side of a building, the overhanging eaves of which 

 shaded the experimental shoots. The weather also previ- 

 ous to and during the experiment was cloudy. Under 

 such conditions it is to be expected that the carbohydrate 

 supply to the shoots would act as a limiting factor. In 

 set B, the plants were growing in the open where they were 

 well illuminated, and the day before commencing the 

 experiment had approximately twice the sunshine. There 

 was fair precipitation during both periods. It is to be 

 noted that, although the total sugar per stem is decreased 

 by ringing, the percentage on the fresh weight basis nearly 

 equalled the check while on the dry weight basis it exceeded 

 it. For the Hhus material, although the ringed stems 

 showed less total sugar than the check stems or those with 

 xylem cut, as did the Philadelphus shoots, they had a 

 distinctly higher sugar content when expressed as per- 

 centage either on the fresh-weight or dry-weight basis. 

 Obviously, therefore, sugar was not a limiting factor and 

 it seems probable that nitrogen or some other soil con- 

 stituent was lacking. These plants also were grown in the 

 open and had received abundant light. 



Since it seemed possible that part at least of the trans- 

 location in these shoots with the xylem removed may have 

 taken place through the cambium layer or through the 

 young cells recently cut off from the cambium and not 

 yet differentiated, one experiment was carried out in which, 

 after severing the xylem, the cambial layer of the bark was 

 thoroughly scraped with a knife. For comparison the 

 phloem was cut in matched stems. In these the cambium 

 was not scraped. The data from such an experiment are 

 presented in Table 8. 



It is evident from this experiment that the cambium is 

 not essential for translocation, nor is a continuity of the 

 cambium essential for growth as suggested by Swarbrick 

 (1928). At the end of the first two-day period the stems 

 with xylem cut had, in all but shoots 6 and 7, lowered the 

 water in the encasing tubes to a point below the cut end 



