The anthracnose fungus of cucurbits produced galacturonoogenic polygalacturonase (GPG) in the case of forming the infection hypha from appressorium, but did not produce it during the conidial germination and appressorial formation. Since this enzyme was secreted by the fungus adaptively into the substrate, this fungus seems to increase GPG production abundantly when the infection hypha forced its way into the middle lamella of cucurbit leaves. The pathogenicity of this fungus of which conidia was suspended in pectic solution showed no great difference from that was suspended in distilled water. The grade of GPG production by the fungus was not affected by the susceptibility of cucumber plants to the anthracnose fungus.
Judging from these results, this fungus seems to have the equall ability to attack the cucumber leaves regardless of the suscept varieties, and the varietal difference in the susceptibility of cucumber plants might be due to the response of the suscept tissue, particularly, of the middle lamella to the pathogen.