332 EAKL S. JOHNSTON 



In plant nutritional studies the more definite the culture 

 medium can be described the greater is the possibility of a true 

 interpretation of results. A nutrient solution is more easily and 

 definitely described than either a soil or sand medium. A solu- 

 tion is therefore more nearly an ideal medium. A sprout from 

 an Irish Cobbler tuber, taken at the stage where its leaves had 

 begun to develop, was placed in a paraffined cork stopper and 

 its roots immersed in a nutrient solution. The plant grew for 

 about two months, but never attained anything like normal size. 

 In the saturated air space between the bottom of the cork stop- 

 per and the surface of the solution several tubers developed. 

 Figure 3 illustrates the appearance of this plant shortly before 

 the end of the experiment. The aerial portion of the plant did 

 not differ materially from those planted in the pots of garden soil 

 (fig. 2). 



Although the results of these two experiments were far from 

 satisfactory in finding a method for successfully studying the 

 nutrient requirements of the potato it was thought worth while 

 to continue the work still further along this same line. 3 Potato 

 sprouts, after being separated from their tubers, were grown in a 

 series of nutrient solutions. Six three-salt solutions were se- 

 lected from those being employed by cooperators with the Na- 

 tional Research Council in the salt nutrient studies of plants. 

 About 60 McCormick potato tubers of approximately the same 

 size and with their first sprouts of uniform appearance and about 

 1.5 cm. long were selected from several hundred stored in a 

 vault. These tubers were planted in moist sawdust in the open 

 on May 16, 1919. On June 5, sprouts of approximately 10 cm. 

 in length with well developed roots and with leaves started, were 

 separated from their tubers. The roots were washed in tap 

 water, then soaked in distilled water for about fifteen hours, 

 after which they were weighed and set in the cork stoppers of 

 solution jars. Each culture comprised a single plant, suitably 

 supported in a quart glass jar filled with a nutrient solution. 

 Most of the light was excluded from the roots by wrapping the 



3 Skinner, J. J., Water culture method for experimenting with potatoes. Plant 

 World 11:249-254. 1908. 



