1. This paper gives the results of studies on the morphological, physiological, and pathological characters of a new fungus that causes the fire-blight disease of the Udo Salad Plant (Aralia cordata THUNB.). 2. This disease begins to appear in the late spring on the leaves, stems, and flowers. On the stem appear brown blisters and ellipsoidal spots; at first small, but gradually enlarging under favourable conditions, sometimes reaching 3-11 x 1-2 mm. in diameter, their shape being usually ellipsoidal or spindle. In very advanced stages of the disease, there appear in the blister a brown to grayish white center, bordered by violet-brown, and small black pycnidia produced on a lesion. The spots on badly affected stems coalesce, often forming a corky surface and atrophy, after which they dry up. On the leaf blade, mid-rib, and petiole of the leaves appear red-violet spots, they wither or shrivel and then dry up. The flowers also wither and die. 3. The pycnidia of the fungus are usually formed under the epidermis of the upper surface of the spot, and the epidermis is perfolated by minute ostioles. The pycnidia, which are spherical or subspherical in shape, measure about 37.5-150.0 μ in diameter and are dark brown in colour. The pycnospores are ellipsoidal, or slightly slender, at one pole, and are hyaline. Their measurements are 3.75-6.25×2.5-3.75 μ. In culture media, the pycnidia are 75.0-300.0 μ in diameter, and their colour black or brownish black, while the external character of the pycnospores are the same as those observed on the affected stems. 4. A single spore isolation was made from an affected stem, and the cultural characters of the fungus were studied with ten different media. It was found that the most suitable medium for mycelial growth was potato decoction agar, while that for the formation of pycnidia and pycnospores was potato decoction agar, Richard's solution agar, and apricot decoction agar. 5. The relation of temperature to the growth of the fungus was studied on apricot decoction agar, Richard's solution agar, and soy agar. It was found that the optimum temperature for mycelial growth was 25°C in apricot decoction agar and Richard's solution agar, and at about 22°C in soy agar, the minimum being below 10°C, and the maximum between 30°C and 35°C. 6. The relation of hydrogen-ion concentration to mycelial growth was studied under different pH for Richard's solution agar, which were prepared by using caustic soda and sulphuric acid. The growth occurred in media, the pH of which were from pH 2.2-3.0 to 8.6<, and at pH 6.8. the most favourable growth was observed. 7. The effect of concentrated sucrose on mycelial growth was studied with Richard's solution to which various proportions of sucrose were added. The most suitable concentration was the addition of 2% sucrose both to the liquid and solid, followed by concentrations of 1% and 5%, whereas any change in the proportion, whether increase or decrease, interfered with growth. 8. The relation of temperature to growth of germ-tubes from pycnospores was studied by sowing them on apricot decoction and kept for 20 hours at different temperatures. The optimum percentage of germination was about 25°C, followed by 28°C and 22°C. At 35°C and 15°C no germination was observed. 9. The relation of hydrogen-ion concentration to growth of germ-tubes from pycnospores was studied by sowing them on Richard's solution of different pH, and keeping for 18 hours at 22°C. Growth occurred in media the pH of which were from pH 1.8-2.2 to 8.6<, pH 6.8 furnishing the best growth. 10. The effect of concentration of sucrose on the growth of germ-tubes from pycnospores was studied by sowing them on Richard's solution and adding to it various proportions of sucrose.
1. Keeping the seedlings of wheat, inoculated with the uredicspores of Puccinia rubigo-vera tritici in moist chamber at various constant temperatures, the developmental features of the fungus presented for infection were observed at intervals, and the critical stage of development at which the infection is warranted was determined. 2. The final results of the inoculation experiments under variousconditions show that the formation of the penetration tube from the appressorium marks the period of infection. Therefore, to obtain infection the inoculated seedlings are required to be kept under a moist condition favourable for the fungus development at least until this stage is attained. 3. At a temperature of about 23°C the urediospores germinated within 1 hour, and appressoria were formed 3 hours after the inoculation. About one third to one half of the germinated spores produced appressoria after the lapse of 7 to 9 hours. Penetration tubes were found occasionally 4 hours after and very frequently from 6 to 9 hours after, whereas 24 hours later a great majority of the appressoria were provided with the tubes entering stomata. Infecting hyphae were produced 9 hours after, developing haustoria about 20 hours after the inoculation. 4. At a temperature of 28°C, the spores were inhibited in germination as well as in further development. At 15 to 25°C appressoria were formed 3 or more hours after, and at 8 to 13°C 6 or more hours after the inoculation. Above 15°C stomatal entry took place 3 to 6 hours after, and below 13°C 9 hours after the inoculation. Above 18°C the haustorium formation proceeded 14 to 24 hours after, but at 8°C the development of infecting hyphae was proceeding even 24 hours after the inoculation. 5. In urediospores, which had been preserved in refrigerator for 158 days, the germination and subsequent development were remarkably delayed in contrast to the fresh ones. In consequence, the stomatal entry took place later than usual. 6. The shortest period for infection was found to be 9 hours at 8 to 13°C, 6 hours at 15 to 20°C, and 3 hours at 23°C. This period coincides with that of the formation of penetration tubes. An abundant infection was obtained when the inoculated surface was kept moist for 14 hours at 8 to 13°C, and for 6 hours above 15°C. 7. Generally speaking, the optimum temperature for the infection of wheat by leaf rust is regarded to range from 18 to 25°C.
1. The sclerotial or Botrytis rots of onions are found very often upon the stored bulbs in the central markets, as well as in the shops of greengrocers in Kyoto and Osaka. In the previous paper, the writers described the gray-mold neck rot caused by Botrytis Allii MUNN, which is most common and causes heaviest losses among them, with special reference to the morphology and the pathogenicity. of its causal fungus. 2. In the present paper, the mycelial neck rot caused by Botrytis byssoidea WALKER, the small sclerotial neck rot caused by Botrytis squamosa WALKER and. also a new disease caused by an undetermined species of Botrytis were described in detail. 3. Although the occurrence of these three diseases seems to be very rare in this country, they have been produced repeatedly by inoculating onion bulbs through needle wounds with mycelium from pure culture and with conidia and conidiophores which developed upon infected bulbs, upon the potato-dextrose agar or upon the sclerotia placed on the sterilized soil in the case of the hitherto undescribed disease. 4. The symptoms of these diseases, as well as the morphology of their causal fungi were first described. The results of the cultural experiments carried out by the writers were then given in detail. 5. It was demonstrated clearly by carefully inoculating the outer succulent scale of a bulb that the most satisfactory method of obtaining infection by B. byssoidea was of course to inject conidia into needle wounds, placing bulbs under conditions in which toorapid desiccation of the wounds is prevented. Under humid conditions and favorable temperature, invasion of the unwounded outer succulent scales has been scarcely noted in a slight degree. 6. A number of experiments were made to determine the relation of temperature to infection by B. byssoidea and the rate of progress of decay. The results show that infection seems to occur in a wide range of temperature ranging from 3°C to 32°C, although the most rapid decay takes place at temperatures from 10°C to 24°C. 7. Even at the most favorable conditions, the decay of onion bulbs caused by B. squamosa progressed much more slowly than in the case of other three species of Botrytis isolated from decaying onions. 8. Many inoculation experiments with the undetermined species associated with onion rot were also performed by the writers. The results show that its pathogenicity seems to be as strong as to penetrate at times the unbroken cuticle of succulent scales. The most favorable temperature for the decay caused by this fungus seems to lie at approximately 24°C. 9. All four species of Botrytis associated with onion rot differeach other not only in their spore-dimension, but also in their cultural characteristics especially on the plate of potato-decoction agar containing 2% dextrose. 10. Inoculation experiments performed by the writers demonstrated clearly, that all the strains of Botrytis cinerea PERS. isolated from decaying fruits of strawberry and Satsuma-orange, and also from lettuce have power to infect the succulent scales of stored onions, when injected conidia together with conidiophores into needle wounds.