Studies on the breeding of trees of special use. (5) : On the yield of bark and the quality of its fiber and paper in the hexaploid Mitumata (Edgeworlhia papyrifera).

In the previous paper the author made an observation on rapid growth in induced hexaploid Edgeworthia papyrifera. Edgeworthia papyrifera is divided into two or three races, an'.ong which Shizuoka-race is t.he most widespread one and Kochi-race is of the most superior quality. They are both tetraploid, but genom constitution are partly different from each other. An octaploid plant of Shizuoka-race was induced by treatment with coicllicine and many hexaploid plants were obtained from its cross with tetraploid. Some economic characters of hexaploid plants were compared with those of Shizuoka and Kochi races. In this investigation four year old plants were used. As can be seen in Table 1, yield of green bark weight and the -white bark (partly refined bark without outer colored layer) ratios m hexaploids were the high st of the other two races. The finai yield of white bark reached more than twice that of Shizuoka-race. The ratio of the effective fibers (Table 2) was also found to be the, highest in the hexaploid. Its fibers were longer than those of the other two races, and thicker in diameter than those of Shizuoka-race, . The strength (the breaking length and the bursting strength ratio) of the paper made from them was measured. The results showed that the strength of the paper made from hexaploid plants was much the others better than that from Sizuoka-race and even exceeded the Kochi-race. In short, the hexaploid plants are qmte supenor not only m thelr yleld of bark or fibers but also in their quality.