In diseased plants of mulberry trees with slight symptom of wilt, we found that the pathogenic bacteria (Pseudomonas Solanacearum) Parasitized not only the vessels of the diseased root,but also the xylem parenchyma cells. Abnormal parenchyma containing large amount of pathogenic bacteria was also observed for the first time. In the stem vessel system, no pathogenic bacteria were found; most of the vessels, however, contained tyloses.