gradually toward Day 120. An average of sugar concentration through the cross section of the disc was calculated by Eq. (1),assuming that the volume ratio of sections A, B and C is 1:3:5. The average concentration calculated at Day 0 was 83 mg ml1 and it became 153 mg ml1 at Day 30 and then decreased to 43 mg ml1 after 120 days as shown in Fig. 4. Although dispersion in average total sugar content was observed among trunk samples, a distinct changing pattern of sugar concentration in sap, that is, an increase during the first 30 days followed by a decrease thereafter, was recognized.