Abstract
Analysis of bark sectors through which tangential movement had occurred showed that sucrose was present in greater quantities than glucose or fructose. No evidence could be gained from such analyses, however, as to which of these three sugars was the mobile species. The use of 14CO2 supplied to the leaves, revealed that after 24 hours of tangential movement, the greatest proportion of the activity in the bark sectors was present in sucrose. By progressively reducing the time during which tangential movement was allowed to occur in these tracer experiments, a pattern of results was obtained which completely supports the assumption that 14C-labelled assimilates are transported in a tangential manner round the stem as sucrose. The presence of activity in glucose and fructose is merely due to their production from labelled sucrose.