Abstract
1) The present paper is a report on a disease of the grape cluster. The studies of the causal orgapism were carried out chiefly on morphological characters of its pycnidium, pycnospore, perithecium, ascus and ascospore, by the writer during 1914-1916.
2) In Japan the disease, of the grape cluster has been prevalent in Okayama prefecture, and also in other few places, where Vitis vinifera is cultivated, since the beginning of the last decade of this century.
3) The disease, while infecting the, cluster, i.e., peduncle, pedicel and berry of Visit vinifera, does not attack the leaf or the stem; and is known locally under the names of “Fusagare” (cluster rot) or “Zikugare” (peduncle rot).
4) The pycnidial stage of the causal fungus of this disease is identical with Macrophoma reniformis (Viala et Ravaz) Cavara, which is known as the cause of the “black rot” in the Caucasus. It perithecial stage is identical with Guignardia baccae (Cav.) Jaczewskii (the perithecial stage of Macrophoma reniformis) except for the fact that the paraphyses exist among the asci in the case of our fungus.
5) The present fungus does not belong to the genus Guignardia, but. to Physalospora. because the existence of the paraphyses in the peithecia can not be denied. Therefore the name Physalospora baccae Cavara (which was changed by. Jaczewskii to the name Guig. baccae is adopted in this report.
6) On such cultural media as boiled potato or boiled rice, this fungus flourishes very rapidly, developing copious black aerial mycelia, and occasionally producing pycnidia.
7) The pycnidia produced on these artificial media are not similar, in their outer appearance, to those found on the host. With regard to the pycnospores, however, the writer find no great difference between them.
8) By the addition of tartaric acid to rice decoction agar (each 1 c. c. of the acid solution between 1/43 and 1/45 molecular to 10 c. c. of the medium) the growth is somewhat stimulated; but tartaric acid solution above M/4 checks it.
9) the parasitism of the present fungus has been fully demonstrated by the previous workers. Our inoculation experiments, however, have not as yet led me to any conclusion.
