I 



102 BOTANICAL GAZETTE [February 





Method 



Culture solutions 



The method of sand culture was used throughout these experi- 

 ments, the sand used being a highly pure Ottawa silica sand obtained 

 from Ottawa, Illinois. Two gallon glazed stone jars were used as 

 the culture vessels, each jar receiving 11.4 kilos of sand. The 

 water content of each jar was maintained at approximately 13 per 

 cent of the dry weight of the sand by means of frequent weighing. 

 ' Tottingham's culture solution was used in diluted form. This 

 solution has the following composition: 



f KNO3— 0.0034 M (0.3437 gm. per liter) 

 Solution A: { KH 2 PQ 4 — 0.0108 M (1 .4692 gm. per liter) 



MgS0 4 — 0.0081 M (0.9750 gm. per liter) 



Solution B: Ca(N0 3 ) 2 — 0.0101 M (1 .6573 gm. per liter) 



Enough of these salts to make 100 liters of culture solution 

 were dissolved and made up to 2 liters, the Ca(N0 3 ) 2 being made 

 up in a separate 2-liter portion in order to prevent precipitation 

 of insoluble calcium salts in the highly concentrated solution. The 

 mixture of these two solutions was designated solution A B, and 

 7 .5 cc. of each of these solutions were added to 1500 cc. of distilled 

 water for the initial dose of nutrient solution. This quantity of 

 nutrient solution was applied to the jars designated in the outline 

 of the scheme of the experiment at the time of planting (March 1). 

 In addition, 0.01 gm. of FeCl 3 was added to each culture one 

 week after sowing. On April 4 each A B culture received a second 

 dose of 7.5 cc. of this normal nutrient solution. All cultures 

 receiving only A B solutions will be referred to hereafter as 

 "normal." 



Solutions lacking in P, N, and K were also made. The amount 

 of salts indicated in the respective tables were dissolved and made 

 up to 2000 cc. with distilled water; 75 cc. of these solutions made up 

 to 1500 cc. were used as initial doses. Similarly, solutions were 

 made up in which the P, N, and K were supplied in one-fourth the 

 concentration of that found in solution A B. 



