Abstract
The examinations of the living potato leaf midribs at the initial period of infection by Phytophthora infestans by means of phase-contrast and polarization microscopes has made clear the following facts: Under phase-contrast microscope, in early stage of the penetration of the pathogen, the resistant variety shows the occurrence of the protoplasmic strands and the acceleration of the protoplasmic current of the infected cells. The migration of nuclei towards the infected parts was recognized both in resistant and in susceptible varieties. The birefringence in the surrounding parts of the diseased spots in the resistant varieties was recognized apparently under polarization microscope. The double refraction was intensified by the treatment with alcohol and was weakened through the strong dehydration by concentrated glycerin and became weak or retarded by the treatment with 4×10-4M DNP solution. From these results, the writer supposed that the stimulation of energy cycle might be concerned with the acceleration of the protoplasmic movement and the appearance of protoplasmic currents of the infected cells of the highly resistant variety. The possibility of the change of micellar structure within protoplasm by the invasion of pathogen in the resistant varieties was also suggested.
