1. As has already been noticed by various investigators, Bact. solanacearum, a causal organism of brown rot of Solanaceae and other plants belonging to different families, is very variable in pathogenicity as well as in morphological, physiological and cultural characters. 2. According to the author's observation made up to the present time, there are at least the following 16 types: “F”. “Op”, “C”, “SS”, “SS'”, “R”, “TRS”, “TRS'1”, “TRS'2”, “TRS''”, “C'M”, “R''”, “C''”, “Cu”, “RS”, and “F''”. 3. The first-named 4 types were isolated from the lesions of tomatoes, tobaccos, eggplants, etc. naturally affected in the fields. Type “F” is a so-called “fluidal” form, which is characterized by having an irregular, fluidal, milky colony; the next one, “Op”, is a so-called “opalescent” form, which is characterized by a circular, homogeneous, opalescent colony; the third one, “C”, is characterized by a circular, light brownish, concentric striate colony, and the fourth one, “SS”, is characterized by a circular, pale fluorite green colony with a cream color centre. 4. The remaining 12 types were originated from the colonies appeared on the agar plates subcultured every 5-7 days by use of the following liquid cultures, i. e. beef extract bouillon, potato dextrose solution, milk, and Uschinsky's solution previously inoculated with the above-named four types. 5. Type “F” is the original form of Bact. solanacearum. Types “Op”, “C”, and “SS” appear to arise from “F” as a result of variation occurred naturally in the tissues of the diseased plants. 6. Type “F” is easily isolable from any young lesions or from the plants in the acute phase of the disease, whereas types “Op”, “C”, and “SS” occur only in a rather advanced stage or in old lesions. 7. All the types are unstable in liquid media except types “R''” and “TRS'1” and easily change to the other types. 8. All the types are liable to the lytic action of the bacteriophage specific for Bact. solanacearum.
1. This paper deals with the results of the writer's experiments on the relation of relative humidity to the infection of the rice plant by Ophiobolus Miyabeanus ITO et KURIBAYASHI and also to the germination of its conidia. 2. After the drops of conidial suspension of the causal fungus sprayed on rice seedlings had dried, these seedlings were kept in desiccators, in which the air had been adjusted to the desirable constant relative humidities by means of using sulphuric acid in various concentrations. Those desiccators containing the inoculated rice seedlings were placed for 18 hours in a room controlled at 25°C., and then the seedlings were removed to a green-house bench. After 5 days, the seedlings inoculated and kept in the air of 100, 97.5, 95 and 92% in relative humidities for 18 hours showed typical lesions of the disease, while the seedlings kept at 89% for the same period remained quite healthy. 3. Small drops of conidial suspension of the fungus and pure water as controls were placed on clean slide-glasses and dried naturally at room temperature. After the drops had dried completely, these slides were placed on supports in PETRI dishes, in which the air humidity had been controlled in various degrees by means of using sulphuric acid. These dishes were kept at 25°C. for 18 hours and then the germinability of the spores in the different air-humidities was tested. The conidia on the slides kept at 92% relative humidity germinated slightly, while those kept at 89% showed no signs of germination. 4. The limitation of the relative humidity in which the disease occurs is, therefore, almost the same as in the case of the conidial-germination of its causal fungus on slide-glasses. It is quite reasonable to assume that no infection of rice seedlings by the fungus takes place in relative humidities lower than 89%, since the conidia are not able to germinate under such conditions. 5. The drying of the conidial suspensions of the causal fungus caused to reduce or retard remarkably the germinability of its conidia. 6. The new conidia were formed on the tips of germ-tubes from the conidia of the causal fungus kept at 25°C. for 18 hours in the relative humidities higher than 97.5%.
Acer trifidum HOOK. et Arn. was introduced from China in 1721, and propagated in our country by grafting on Acer crataegifolium SIEB. et ZUCC., it is familiar to us now. For the last 25 years an epidemic disease of this tree has been noticed in the nursery and avenue, but its cause remained quite unknown. In the last year I had occasion to study it and found that this disease had been caused by a species of bacteria. As a macroscopical symptom, there appear on the leaves irregular spots along the midribs. The spots give at first a water-soaked appearance and, increasing in size, become pale payne's gray or black. Meanwhile affected leaves wither and then, turning black, finally dry up, just like those injured by frost. Inoculation experiments on the healthy leaves with the organism isolated from the tissue of diseased portions resulted in giving rise to the same symptom, and the same organism could be obtained from the affected tissue. The following species of Acer were proved to be susceptible to this organism; viz., Acer saccharinum L., A. diabolicum BLUME, A. Negundo L., A. aizuense NAKAI, A. palmatum THUNB. var. amabile KOIDZ. subvar. Kagiri KOIDZ., A. capillipes MAXIM., A. insulare MAKINO, A. parviflorum FRANCH. et SAV., A. pictum THUNB. var. typicum GRAF V. SCHW., A. rufinerve SIEB. et ZUCC., A. Sieboldianum MIQ. var. typicum MAXIM., A. Shirasawanum KOIDZ., A. crataegifolium SIEB. et ZUCC. Besides these, Aesculus turbinata BLUME and Koelreuteria paniculata LAXIM. were also infected with the said disease, but the following plants were not attacked by it; viz., Ginkgo biloba L., Juglans Sieboldiana MAXIM., Ulmus parvifolia JACQ., Morus alba L., Euptelea polyandra SIEB. et ZUCC., Cercidiphyllum japonicum SIEB. et ZUCC., Liriodendron Tulipifera L., Liquidambar formosana HANCE, Prunus yedoensis MATSUM., P. Mume SIEB. et ZUCC., P. spinulosa SIEB. et ZUCC., Phaseolus vulgaris L., P. radiatus L. var. aurea PRAIN, Lathyrus odoratus L., Evonymus striata LOES., E. oxyphyllus MIQ., Staphylea bumalda DC., Euscaphis japonica PAX., Sapindus Mukurossi GAERTN., Berchemia racemosa SIEB. et ZUCC., Hovenia dulcis THUNB. var. glabra MAKING, Zizyphus vulgaris LAM. var. inermis BUNGE, Vitis vinifera L., Tilia japonica SIMK., T. Miyabei JACK. and Firmiania platanifolia SCHOTT et ENDL. The causal organism is rather short rod-shaped Shizomycete with round ends, measuring 0.5-1.2×0.2-0.6μ, usually 0.8×0.4μ, when stained by carbol fuchsin from a 24 hour culture on standard agar, on which it occurs solitarily. It is aërobic and motile by means of one polar flagellum. No spores are formed and no involution forms have been observed even in culture 6 months old. It stains easily with basic anilin dyes and by Gram's stain. It grows on ordinary culture media, viz, , nutrient agar, glucose agar, serum agar, potato agar, steamed potato, nutrient gelatin, bouillon, peptone water, Uschinsky's and Cohn's solutions. On the poured plate of standard agar, the colonies are round, smooth, convex, white, glistening, translucent and entire-margined with amorphous structure. On agar slant, the same filiform streak mentioned above is produced along the inoculated line in 24 hours at 32°C. After 2 days the colour of the streak changes to citron yellow. It liquefies gelatin in cup shape, clears milk slowly without coagulation, produces acid slightly but does not produce gas in fermentation tube from peptone water with saccharose, lactose, maltose, dextrose, laevulose, galactose, mannit and glycerin. It reduces nitrate to nitrite and produces hydrogen sulphide.