Nutrients 



L13 



Pig. 34. At the top, a healthy excised tomato root at the end of 

 a one-week passage. In the second row a similar root lias been 

 divided into eight pieces to be used in setting up a stock of com- 

 parable root tips for experimental use. The ninth, apical piece was 

 discarded. Third row, eight root segments similar to those shown 

 above after a second week's cultivation in fresh nutrient. At the 

 bottom are 32 selected root tips, all derived under comparable con- 

 ditions from the single apex used as inoculum two passages earlier. 



