346 University of Californid PiihJicdtions in Aarirnltur(il Sciences [Vol. 1 



a eoliiiiin of the sand for a period of twenty-four hours. The 

 excess of taj) water retained by the sand was in turn washed out 

 with distilk'd water. While this sand is inferior to the best 

 grade of pure quartz sand in freedom from inorganic material, 

 it is unable to supply available nutrient elements in sufficient 

 quantity to cause any perceptible increase in growth (pi. 14). 

 Two thousand gram portions of the sand treated as above were 

 weighed into six-inch flower-pots which had been previously 

 prepared by dipping them into melted paraffin. The paraffining 

 effectually closed the pores and prevented the absorption of the 

 culture solution by the pot. 



Distribution of Nutrient Salts 



The pots were divided into three different groups designated 

 as series I, II, and III, each series consisting of twenty pots 

 divided into groups of five pots each, and a duplicate in each 

 case, making forty pots in all in each series. In series I, nitrogen, 

 as NaNOa, was the varying factor within each group, the weight 

 of each of the other salts being held constant. Thus, in series I, 

 the pots 1 to 5 in each of the four groups contained NaNO^ as 

 follows: 0.02, 0.2, 1.0, 2.0, 3.0 grams. In a similar manner phos- 

 phorus and calcium, as Ca(H.P04)., were varying factors in 

 series II, while in series III potassium, as K^SO^, was varied. As 

 noted above, the twenty plants of each series were divided into 

 four groups designated respectively as A, B, C, and D, each group 

 consisting of five plants and a control for each. The weight of 

 one varying factor remained the same in pots of like number 

 through all four groups. Thus plants lAl, IBl, I CI, and 

 I D 1 each contained 0.02 grams of NaNO,, and I A 2, I B 2, I C 2, 

 and I D 2 contained 0.2 grams of NaNO;,. But from group A 

 to D the weight of the other nutrient factors decreases, so that 

 group D contains two-thirds, C one-half, and D one-fourth the 

 weight of each of these nutrient factors as present in the A group. 

 The effect of this distribution of salts is to give at least three 

 important variables. First, the single nurient salt in increasing 

 proportions from plant 1 to plant 5 in each group, and second, 

 the factor of total concentration which decreases from group A 



