1. Field observations showed that when cucumber (Cucumis sativus L.) had been severely infected with downy mildew, squash (Cucurbita moschata DUCHESNE) in the adjoining plot was free from, it, suggesting that the fungus on cucumber might be a biologic species different from that on squash. 2. Cucumber, squash, and also several wild and cultivated Cucurbitaceous plants were inoculated with the fungi from cucumber and squash, atomizing with a suspension of sporangia or placing drops of a suspension on the under surface of the foliage. 3. Some spots and in a rare case sparse sporangia were produced on the squash inoculated with the fungus from cucumber by the latter method described, but neither spots nor sporangia by the former method. On the other hand the fungus from squash infected cucumber to produce not so much spots and sporangia as on squash by both inoculating methods. 4. Other plants inoculated showed similar reactions to both fungi respectively except Actinostemma lobatum MAXIM. var. racemosum MAKINO on which sporulation was secured with the fungus from cucumber alone. 5. The angular spots characteristic of downy mildew on cucumber were measured 4.7×3.4mm. or 5.3×3.7 mm. in average size according to the samples, while the spots of squash were distinctly small, 1.6×1.0 mm. on the average. 6. The downy spots on cucumber, muskmelon, and oriental pickling melon artificially infected with the fungus from squash were indistinguishable in size from those on squash. 7. From the results of the present experiments it is undoubtedly concluded that the fungi from cucumber and squash are biologic species different from each other. 8. In the fields, besides the angular spots the author observed the occurence of downy spots on cucumber which extremely resembled those on squash in appearence but little sporulation. These spots of cucumber might presumably be caused by natural infection with the fungus from squash.
1. This paper gives the results of studies on the symptoms of the sclerotial disease of narcissus, and the morphorogical and physiological characters of the causal fungus. 2. The symptom of the diseased narcissus appears at first as yellowing of the tips of leaf blades which gradually spreads to whole plant with the appearance of very small sclerotia on the outer skin of bulb. If the infected bulb is planted in the following year, it shows a very poor growth of premature yellowing of the leaf blades. The bulb finally contracts by drying and dies. 3. The sclerotia of the fungus are spherical or subspherical in shape, black or dark brown in color, and measure 80-70×165-121μ in diameter on the host. The microconidia are spherical, smooth and measure about 2.0-2.5μ in diameter. Apothecia are not produced. 4. The cultural characters of the fungus were studied on ten different media. It was found that potato, bean, SAITO's soy onion, and CZAPEK'S agars were suitable for the mycelial growth; while potato, bean, CZAPEK'S, RICHARD's, and apricot agars at 20°C. for the formation of sclerotia. 5. The relation of temperature to the growth of the fungus was studied on ten different media. It was found that the optimum temperature for mycelial growth was 28°C., the minimum below 0°C, and the maximum between 32° and 36°C. 6. The relation of hydrogen-ion concentration to the mycelial growth was studied on potato agar. The growth occurred in media ranging from pH 1.9 to 10.1, and the pH 4.8 was observed to be most favorable. Sclerotia were produced at every concentrations, but were produced later at high and low ends of the pH and fewer in number at high concentrations. 7. The relation of sucrose concentration to the mycelial growth was studied on potato agar medium. The best concentrations were between 5 and 7%, but fair growth was observed even at 30%. In both high and low concentrations, there was a tendency for the growth of the fungus to decrease rapidly. Sclerotia were produced abundantly only on non-sucrose medium, and as the sucrose concentration increases, it interfered with the formation. When the concentration reached 7% or more no sclerotia were formed. 8. The relation of NaCl to the mycelial growth was studied on onion agar. The most favorable growth was noted on the medium in which no salt was added. An increase in salt concentration interfered with the growth. It was entirely stopped at 8% concentration. The sclerotia were formed only on the saltless medium. 9. Narcissus, tulip and onion bulb, gladiolus corm can be infected artiicially by inoculating them with the fungus mycelium. The disease is specially manifested when the fungus is introduced into the soil. 10. The viability of the causal fungus was observed to be about two years in test tubes. 11. According to my study, there are 12 varieties of narcissus that can be infected with the disease. 12. In connection with the import plant inspection work, this fungus was first noticed at Yokohama port in 1928 on the diseased tulip bulbs imported Crom Holland, and ever since, it has been intercepted at various parts of Japan proper. 13. This causal fungus is identical with Sclerotinia gladioli (MASS.) DRAVIDSON, causing the dry rot of gladiolus.
1. In the lesions of the rice blast disease, an yellow bacterium is associated very often with its causal fungus. 2. It has been decided by the writer that the group number of this yellow bacterium is Bac. 211, 2222532. 3. The diagnosis of the bacterium is as follows: Motile by peritrichiate fragella; 2-2.4×0.5-0.7μ in size; oblong or short rod in shape; no capsule; Gram positive; aerobic; optimum temperature 28°-30°C; maximum above 40°C; minimum between 10°C and 16°C. 4. The inhibition in the mycelial growth of the causal fungus was not recognized in the mixed culture, in which the fungus and the bacterium were transplanted to confront each other, but the conidial germination of the former is influenced by the presence of the latter. 5. Although the co-existence of the bacterium with the causal fungus is apt to inhibit the occurrence of disease on the rice seedlings, the enlargement of the spots seems, however, to be little influenced. 6. In the co-existence of the bacterium, the conidial germination of the causal fungus and also the occurrence of the disease are more or less inhibited. However, such inhibiting action of the living bacterium is remarkably weakened by its sterilization. The reason of the above facts is not yet determined.