PLANT BACTERIA, VOL. 2. 



PLATE 3. 



Black Spot of the Plum. 



(1) Surface of a green plum (x 10), showing a white speck (stoma) in center of a very small spot, due to Bact. pruni. 



This is the earliest stage of the disease clearly visible to naked eye. Each of the numerous white specks has 

 a single stoma in its cent?r. 



(2) One of the tiny white specks more highly magnified so as to show the central stoma. x 200 (?] 



(3 and 4) Two sections through a normal stoma on the green fruit, showing empty sub-stomatic chamber; one 



passes through the center, x 200 (?). 

 (5) A group of small spots on a green Hale plum, each of the smaller ones showing clearly a stoma in its center. 



(6 and 7) Small spots (x 10) showing bacterial exudate. Spots further advanced than in fig. i . In fig. 6, bacteria 

 were issuing from 30 or 40 stomata, but, as in fig. 7, the central drop is larger. The reason for this is apparent 

 at once on cross-section (see plate 5). 



