204 



Journal of Agricultural Research 



Vol. XIX, No. 5 



and their manner of occurrence indicates that wounds are not necessary 

 for infection. They are commonly to be found upon branches as large 

 as 2 or even 3 inches in diameter, the wood of which has entirely hardened 

 and matured. One case has been observed of such cankers on the trunk 

 of a lime tree 6 inches in diameter. Such cankers have never been seen 

 on species other than the lime, the sweet orange, and the grapefruit. 

 Cankers occurring in this way do not cause the killing of the limbs or 

 branches, their seriousness consisting chiefly in affording constant sources 

 for reinfection of foliage and fruit. Such cankers are also easily over- 

 looked, inasmuch as they are small and of the same color as the nor- 

 mal bark. 



The presence of such cankers suggested that cankers might also occur 

 upon the roots of trees. . Inoculations were therefore attempted upon 

 roots with P. citri by means of needle punctures. The inoculations 

 reacted slowly, but in 30 days examination showed that some of the 

 punctures were undoubtedly positive. Control punctures with tap water 

 were negative. The inoculations were then made repeatedly. The best 

 series of results is selected here for presentation in Table IX.. A pho- 

 tograph (PI. 37, A) also shows some of these results. Mature trees, ac- 

 tively growing and thrifty, were selected for inoculation. 



T.-VBLE IX. — Results of inoculations with P. citri by means of needle punctures into 



roots of Citrus sinensis 



Inocu- 

 lation 

 No. 



119 

 120 

 121 

 122 

 123 

 124 



126 



127 

 128 

 129 



132 



134 



135 



136 



137 



Inoculum. 



P. citri culture. 

 do 



do 



do 



do 



do 



do 



do 



do 



do 



Tap water. 



do 



do 



do 



do 



do 



do 



.do. 

 .do. 

 .do. 



Dia- 

 meter 



of 

 root. 



Mm. 



Date of inocula- 

 tion. 



Dec. 5, 1917 . 

 ....do...... 



do 



....do 



...do 



....do 



....do 



....do 



....do 



....do 



....do 



....do 



...do 



....do 



....do 



....do 



...do 



.do. 

 .do. 

 .do. 



Date of examina- 

 tion. 



Positive ' Feb 



do 



do 



do 



do 



do 



do 



do 



do 



do 



Negative 



do 



do 



do 



do 



do 



Swelling (no 



eruption). 



Lost 



Negative 



....do 



• 15' iQii 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 



Do. 

 Do. 

 Do. 



The inoculations were made with a needle, and the punctures were 

 covered with moist cotton and wrapped in paraffin paper, then in opaque 

 paper, and covered with earth. 



