The microscopic investigations were carried out on the process of infection of Colletotrichum Lindemuthianum Briosi et Cavara to the bean varieties being resistant or susceptible to the anthracnose. The observations have been performed upon the appressoria formation of the fungus on the epidermal tissue of bean plants, and upon the invasion and further development of the hyphae in the host tissues as well as the causal morbid changes of the cell-tissues. In the experiments we have used the D-strain of bean anthracnose fungus as the inoculum, and two susceptible varieties i. e., Tenashi-naga-uzura Hon-Kintoki and 5 resistant varieties i. e., Tenashichunaga-uzura, Satisfaction, Indian Chief, Beni-kintoki, O-tebo. On the susceptible varieties, Tanashinaga-uzura and Hon-kintoki, large sunken reddishbrown lesions having numerous acervuli were formed on the inoculated tissues, while on the resistant varieties, Tenashi-chunaga-uzura, Satisfaction and Indian Chief, very small reddish-brown lesions appeared. In the cases of the highly resistant varieties, Beni-kintoki and O-tebo, no lesion was recognized by naked eyes. The appressoria formation and invasion of the hyphae occurred equally on both susceptible and resistant varieties. More than 70% of the appressoria were formed on the part of middle lamellae of epidermal cells. The protoplasmic morbid changes occurred in the resistant plants, Tenashi-chunaga-uzura, Satisfaction and Indian Chief, were induced very rapidly by invasion of the hyphae and the cells surrounding the point of infection turned brown remarkably. However, the further development of the mycelia in the tissues was checked in general, and the lesions appeared as only very small reddish-brown spots. The similar phenomena were observed in the cases of highly resistant varieties, O-tebo and Beni-kintoki, and the lesions were far more minute owing to fewer number of the browned cells. These minute lesions formed on the highly resistant varieties were almost invisible macroscopically. On the other hand, the protoplasmic morbid changes in the susceptible varieties progressed slowly, and no marked symptom was recognized until the mycelia had developed widely in tissues, and severe destructions of them took place rather suddenly.
The present paper deals with the results of experiments on a dwarf disease of milk vetch (Astragalus sinicus L). The results obtained are summarized below:- I An infested plant discolors yellowish green to dull yellow and stunts as a whole and its leaflets become small and narrow. Margin of the leanet is often colored reddish purple. Later on, necrotic lesions develop often on Ieaflet, petiole and stem. Most of flower buds of the severe1y infested plant drop down before blossoming. Slightly infested Plants may bloom but the seeds do not ripe perfectly. In case of severely infested plants, the lower leaves dry up from the margin of leaflets and finally, the whole plant die prematurely. 1. Causal agent of this disease was found to be a virus. 2. 4 species of aphids i.e. Aphis laburni Kaltenbach, A. glycines Matsumnura, Macrosiphum Pelargoni Kaltenbach and Myzus persicae Sulzer were tested for transmissibility of the virus and only the first named species of aphid proved to be a vector. 3. Aphis laburni became infective when it was fed on the diseased plant for 24 hours and the virulent aphid was able to transfer the virus to the healthy plant by feeding for more than 6 hours. 4 The infective aphid was able to transfer the virus through its who1e life. 5. The virus was not transferd to viviparous offsprings from the infective parent aphids. 6. The writer failed to obtain successful transmission by mutilating with the diseased plant juice. 7. The transmission of this virus through the seeds was not determined distinctly. 8. This virus seems to be some what differerent from the red clover mosaic virus or common bean mosaic virus. With regard to its identification further investigation is needed. II this disease was found to be distributed in the prefectures, Yamagata, Fukushima, Niigata, Nagano and Ibaragi.