Anthracnose of Digitalis was recorded in different parts of Europe and in Nippon, and a confusion took place as to the causal organism. The disease occurs on the leaf as small purplish brown, round or unsharply angular spots, dispersed over the leaf. The spots do not enlarge markedly and remain usually about 1 mm in diameter (Fig. 1, left and center), but sometimes spots of irregular shape, 3-4mm in diameter, are produced (Fig. 1, right). On the large veins and petiole, small, spindle-shaped, sunken, blackish brown lesions are formed. The central part of the old spots discolors to light brown, and is provided with minute black dots (Fig. 2). On diseased leaves a dead portion appears first over severely infected parts, finally extending to their whole area. Acervuli amphigenous, pulvinate or disciform, 24-120μ in diameter, often confluent. Conidiophores on pseudoparenchyma, hyaline, rod shape tapering towards the tip, with about an equal length to conidia. Conidia continuous, hyaline, granulous, long elliptic to cylindric, blunt at both ends or unsharply pointed at an end, straight or slightly curved, 13-21×3.5-4.5μ. Setae dark brown, long (75-120μ), broaden at the base (4.5-7μ in width), often nodular, about 4μ in width at the middle, taper and become hyaline towards the tip, straight or flexuose, 3-5 septate, produced numerously, for instance 2-24 to a section of a single acervulus. (v. Fig. 3) The fungus grows well on agar media. A certain strain produces acervuli with setae and conidia in culture, while other olivaceous mycelia only. On inoculation, they can infect unwounded leaf blades and petioles and semetimes causing damping-off of seedlings (Fig. 4). Four species of anthracnose fungi have hitherto been reported on Digitalis (Gloeosporium Digitalis E. ROSTR., Colletotrichum fuscum LAUBERT, C. digitalis (E. ROSTR.) MOESZ, and C. digitalis UNAMUNO). Of these, C. Digitalis differs from the fungus in question, as the former associates with large, dark brown maculae, lacks setae which are so prevalent in the latter, and produces much smaller conidia (8-10×3-4μ)., While the remaining three, in despite of a certain discrepancy, are alike one another, C. fuscum and the fungus in question agree almost completely in essential characters (v. Table). The name C. digitalis by UNAMUNO is illegitimate since it was previously used by MOESZ. The morphological characters of MOESZ's C. digitalis approach more closely to C. fuscum than G. Digitalis, though he mentioned it as being a form of the latter which has well-developed and provided with setae. In Nippon, FUKUI (1933) studied this disease, identifying the causal fungus tentatively with C. Antirrhini. However, TAKIMOTO in Kyûsyû Imperial niversity ascertained that our fungus cannot infect snapdragon. At present it may be concluded that the anthracnose fungus of Digitalis in question is identical to C. fuscum LAUBERT, that C. digitalis by UNAMUNO is a synonym of it, and that the fungus named C. digitalis by MOESZ is probably a form of the same.
1. Using several species of wood-destroying fungi, the respiration of each fungus on various media was determined. And from the results of the respiration intensity shown by the fungi, the utilization of the carbon sources in the media is discussed. 2. Sugars both hexoses and pentoses, are utilized as metabolic substances by all the fungi used. 3. Phenolic compounds are mostly toxic for the fungal metabolism. Among them, catechol, chinon, salicylic acid and benzoic acid showed severe toxicity for all the fungi. On the other hand, some compounds appeared to be utilized by certain fungi. For example, para hydroxybenzoic acid is toxic for Polyporus japonicus and also for P. Schweinitzii, but efficiently available for Polystictus sanguineus. This fact shows that the wood-destroying fungi can decompose the benzene nucleus and consume these aromatic compounds as their metabolic substances. 4. Wood-destroying fungi can generally respire in an anaerobic condition. So far as the present experiment goes, the anaerobic respiration shown by cellulose-specialists is greater than that of the lignin-specialists.
1. The effect of four different intensities of sunlight upon the enlargement of the diseased lesions on the leaves of rice seedlings caused by Piricularia Oryzac BR. et CAV. was investigated. In the experiment the writer used the glass boxes kept under the same conditions except light intensity. The potted rice seedlings were kept in the boxes uncovered, covered with a single or two sheets of white cotton cloth and also with black paper as soon as they had been taken out from the inoculation chamber. After previously determined intervals the length and width of the diseased lesions were measured with the aid of a divider. 2. Judging from the results of the writer's experiment, the degree of the lesion enlargement soon after the incubation period seemed to be maximum on the seedlings kept under a weak shading and minimum on those in the darker boxes. The seedlings, kept in the lighter boxes than the former, showed the medium degree of enlargement. 3. The above relation of shading to the lesion enlargement changed gradually with the lapse of time and in the later period the lesion enlargement on the seedlings kept in the lightest boxes became maximum. It is recognized that the darker the boxes are, in which the seedlings grow, the smaller the lesions become. 4. The influence of sunlight upon the growth of the causal fungus on the potato decoction agar containing 1% sucrose was investigated under different light intensities controlled as same as the previous experiment. The results of the experiment show that the darker the light condition is, the better the causal fungus grows, although the growth difference is not remarkable. 5. The relation of shading to the lesion enlargement soon after the incubation period is thought to be due to the direct effect of sunlight on the growth of the causal fungus, and also to the indirect effect caused by changes in the host vitality. 6. The relation of shading to the lesion enlargement in the later period is thought to be clearly due to the diminution of the assimilation products of the host, which affect the growth of the causal fungus.