junei,i92o Behavior of the Citrus-Canker Organism in the Soil 199 



Table VI. — Inoculations on young pummelo leaves from infusions of autoclaved soil in 

 a box made on consecutive days after inoculation with P. citri. The inoculated soil 

 was placed in the orchard to simulate field conditions — Continued 



X „ -M^ ; Infusion 



Leaves No. j ^^j^^ ^-^^ 



Number 



,?/„^?fA.I Date of inoculation 

 alter inoc- „„ t^.,..^ 



, J.. 1 on leaves, 



ulation I 



into soil. 



Infections from 200 

 punctures. 



Date of 

 observation. 



126 to 130 

 131 to 135 

 136 to 140 

 141 to 145 



146 to 150 



151 to 155 

 156 to 160 

 161 to 165 

 166 to 170 

 171 to 175 



26 



27 

 28 

 29 



31 



3^ 

 33 

 34 

 35 



10 

 10 

 10 



Oct. 



.do. 

 .do. 

 .do. 

 .do. 



1918 



100 per cent positive . 



....do 



....do 



76 per cent positive . 

 100 per cent positive. 



Nov. I, 1918 do. 



do do. 



do I do 



do j 99>^ per cent positive . 



do ! 100 per cent positive . 



Nov. 3, 191S I do 



.... do ' 83>2 per cent positive . 



. . . .do. ...;... I IOC per cent positive . 



. . . .do 93^2 percent positive . 



.... J.; I 96 per cent positive . 



.do. 

 .do. 

 .do. 



^, 191S 



100 per cent positive . 



do 



. QO. 



.do. 



Nov. 9, 191^ 

 Do. 

 Do. 

 Do. 

 Do. 



Nov. 20, 191J 

 Do. 

 X>o. 

 Do. 

 Do. 



Do. 

 Do. 

 Do. 

 Do. 



Do. 



Do. 

 Do. 

 Do. 

 Do. 

 Do. 



SUMMARY OF EXPERIMENT III 



It will be seen that inoculations made from the untreated soil were 

 highly positive on the first day following inoculation wdth P. citri. On 

 the second day there w'as a slight diminution of the positive results, and 

 on the third day the percentages of positive results were very much 

 lower. On the fourth day the larger part of the inoculations were 

 entirely negative. On the sixth, eighth, tenth, twelfth, and fourteenth 

 days following inoculation, all inoculations were entirely negative. 

 That is, six days after the inoculation with a heavy infusion of P. citri 

 in untreated soil, 170 leaves were inoculated, each with 40 punctures, or 

 a total of 6,800 punctures; all remained negative. At the same time 

 inoculations made on consecutive days following inoculations of auto- 

 claved soil with P. citri were highly positive the first day, increased to 

 almost uniformly 100 per cent positive results on the second day, and 

 continued at 100 per cent for 14 days. 



The full significance of this may perhaps be grasped more readily by a 

 brief recapitulation. A dense infusion of virulent active canker organ- 

 isms was heavily inoculated into a box of soil entirely untreated and but 

 recently removed from the orchard. This box of inoculated but otherwise 

 untreated soil was kept under orchard conditions during the experiment. 



