(1) This paper deals with the comparative studies on the meiotic division and the morphological characters of the Shikikitsu, a diploid form, and the Shikinarimikan, a tetraploid form of the citrus fruit. Both forms belong toCitrus microcarpa BUNGE. (2) In the Shikikitsu, normal division takes place, which results theformation of almost fertile pollen grains, while, in the Shikinarimikan, oftenirregular division takes place, which produces finally inuniform pollen grains, about 30 per cent of which are sterile. (3) In both forms, very interesting phenomenon is observed in the modeof conjugation of chromosomes which suggests that the genom of Citrus isof the nature, bearing a constitution like AAA BB CC D E (Fig. 1-9). (4) The appearence of plant and the quality of fruit of both forms do notshow a great difference, excepting that the Shikinarimikan is characterizedby having various organs and cells of various tissues of larger size. (5) Karyological and morphological data obtained in the present studyhave proved that the Shikinarimikan is an autotetraploid form orginatedfrom a certain form closely related to the Shikikitsu or directly from theShikikitsu itself (Fig. 10). (6) The discovery of the occurrence of tetraploid form in cultivated citrusfruits will open a new field in the breeding of new type in Citrus, since wecan expect to create triploid hybrids, by crossing diploid and tetraploidforms, which will produce desirable seedless fruits. (7) Author succeeded to obtain several seeds by a cross between the Shikikitsu and the Shikinarimikan in the course of this year's experiment at Taihoku.
Potted plants of several sorts, such as persimmons, peacnes, Japanese pears, American grapes, beans, soy-beans, and Azuki-beans, were sprayed with Bordeaux mixtures of 6-1.5-100, 6-6-100, or 6-18-100, After spraying, a half of each treat ment was brought into glass house and the other half was left on in the field. After rain fall Bordeaux injury appeared on the leaves of sprayed plants left in the field, but no injury occured on the plants under glass so far as they stay there. After they had taken out in the field, Bordeaux injury appeared similarlly on them. The injury was severest on the plants sprayed with 6-1.5-100 Bordeaux and slightest on the plants sprayed with 6-18-100 Bordeaux. Some plants sprayed with hydrated lime only were free from injury. Persimmon leaves were painted with 6-6-100 Bordeaux. The injury was induced on the leaves whose both surfaces or upper surface only were painted. No injury was induced on the leaves whose lower surface only was painted. The leaves reversed after being painted the upper surfaces only were also free from the injury. As the results of the above experiments seemes to indicate that Bordeaux injury is induced after the sprayed surfaces were wetted by the rain water, the sprayed surfaces of persimmons and buckwheat were wetted artificially with reserved rain water, and after this treatmente for 14-24 hours, typical Bordeaux injury was observed on the wetted surfaces of the sprayed leaves. These facts are favourable to the assumption that the rain fall induces Bordeaux injury on the sprayed leaves of plants. It seems that the rain water is necessary to solubilize the copper in the Bordeaux mixture and solubilizing action of the rain water is a little stronger than that of the distilled water, as the injury on the plants wetted with the former is severer than that on the plants wetted with the latter.