. Bacteria in relation to plant diseases. Bacteriology; Plant diseases. BLACK ROT OF CRUCIFEROUS PLANTS. 307 firms infection by moUusks and reports successful transmissions by aphides. He recovered a yellow Schizomycete from the body of an aphis which had punctured a diseased spot, and with this organism he induced the disease on sound plants. A curculio (Coiitrachelits), which lays eggs in the stems of young cabbage plants, is also open to suspicion. Any creature which gnaws diseased leaves or stems and then gnaws or even crawls over healthy ones is very likely to transmit the infection. It i
. Bacteria in relation to plant diseases. Bacteriology; Plant diseases. BLACK ROT OF CRUCIFEROUS PLANTS. 307 firms infection by moUusks and reports successful transmissions by aphides. He recovered a yellow Schizomycete from the body of an aphis which had punctured a diseased spot, and with this organism he induced the disease on sound plants. A curculio (Coiitrachelits), which lays eggs in the stems of young cabbage plants, is also open to suspicion. Any creature which gnaws diseased leaves or stems and then gnaws or even crawls over healthy ones is very likely to transmit the infection. It is desirable that further studies should be made, especially on plants in the seed-bed and soon after transplanting, particularly with reference to underground infection. Wounds are not necessary, however, for the transmission of this disease, nor do the majority of cases arise as a result of trauma. The greater part of the infections (.Smith, Russell, Hecke) unquestionably take place through certain natural openings of the plants, known as water-pores. These are modified stomata which occur in groups on the teeth of the leaf and through which excessive moisture taken up l.)y the root- system is extruded from the plant. When the air is warm this moisture is given off as an in\'isible vapor, but during cool nights it gathers on the leaf-serratures in drops like dew, and may persist for hours after sunrise. It was experiments with slugs which led the writer to the discovery of water-pore infections. On leaves which had been bitten and infected by AgrioUiuax, a few belated infec- tions appeared on the leaf-margins where no wounds could be detected. A study of these infections showed that they began in the leaf serra- tures. This placed the question of natural infection in a wholly new light and led to further experiments with the results already known (vide Centralb. f. Bakt. 2 Abt., 1897, page 411). Up to the time of the preparation of that paper the writer had not studied this di
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