The authors have made the above researches into the allyl mustard oil, the pungent substances of Wasabi (Eutrema Wasabi, Maxim.), with a view to contributing to the improvement of the cultivation method of the said plant in Shimane Prefecture, and they summarize their present views as follows :
1. The amount of allyl mustard oil contained in each part of the whole Wasabi plant was noticed to exist in the following order :
Root-stocks > Root-hairs > Leaves > Leaf-stems.
2. As regards the seasonal variation of the quantities of allyl mustard oil in the root, the writers have certified the " Winter Wasabi " contains twice as rich allyl mustard oil as the " Spring-Wasabi," and that the amount of the oil diminishes markedly with the blooming period. (as 0.17 : 0.09).
3. The authors have noticed that the allyl mustard oil is most richly concentrated at the upper-middle part of the root-stock and also that the lower end of the root contains the smallest amount. This fact seems to support the validity of the popular belief that the root-stock of Wasabi should be crushed on the grate from the top.
4. In the analyses of allyl mustard oil after crushing of the Wasabi-roots the writers have perceived that higher values are obtained in proportion to the shortness of time for which each sample is kept standing. Since there exist no literature regarding this last mentioned point, the authors would like to make further researches in details in the future. (3. XI, 1957).