100 T. Lyttleton Lyon and James A. Bizzell 



of the primary plants. These will be termed the " secondary " plants or 

 crop. In some cases the secondary plants were planted at the same time 

 as the primary. 



For the purpose of checking the experiments in which soil was used for 

 growing plants, a series of tests were made with crushed quartz containing 

 about thirty per cent of its weight of nutrient solution. This solution had 

 a density of 4500 parts per million. 



Glazed earthenware pots of a capacity of one half gallon were filled with 

 the quartz and the nutrient solution, and four to twelve plants, depending 

 on the size, were grown as a primary crop in each pot. The secondary 

 crop consisted of twice as many plants. The moisture content was main- 

 tained by weighing the pots two or three times a week and adding distilled 

 water in sufficient quantity to make up the loss. Nutrient solution was 

 added two or three times in the life of the plants. It was intended to have 

 an abundant supply of plant nutrients, especially nitrogen in the form of 

 nitrate. The object in using the nutrient solution was to furnish a medium 

 in which the secondary crop could be of no assistance as a means of supply- 

 ing nitrate nitrogen. 



In both the soil and the crushed quartz, the squares and the pots planted 

 with the primary and the secondary crops were in each case accompanied 

 by similar receptacles planted with the primary crop alone and containing 

 exactly the same number of plant's as were present as a primary crop in the 

 vessels containing the primary and the secondary, or what will be termed 

 the mixed, crops. The yields of the plants growing alone may thus be 

 compared with the yields of the primary plants in the mixed crops, as a 

 measure of the effect of the secondary crop on the primary crop. 



The plants growing in the mixtures were always at a disadvantage 

 because there were always three times as many plants in the mixed crop as 

 in the single one. In order to offset this it was intended to furnish an 

 abundant supply of nutriment, but in the greenhouse soil this was probably 

 not fully accomplished. In the nutrient solution some of the mixed crops 

 possibly lacked nutriment. 



The tests in the greenhouse soil in which the primary and the secondary 

 plants were started at the same time did not give very satisfactory results, 

 as the secondary crops grew so large that they perceptibly dwarfed the 

 primary crops except in a few cases. This, however, was anticipated, and 

 such mixtures were used only as checks. In the quartz cultures the prj- 



