1917] Ayres: Nutrient Solution on Plants Grown in Sand Cultures 357 



respectively. The maximum weights of the other salts were 

 NaNOg, 3 g. ; K.SO^, 2.4 g. ; MgSO,, 0.96 g., in group A, while the 

 minimum quantities of these salts as added in group D were 

 0.75 g., 0.6 g., and 0.24 g., respectively. The total concentration 

 in this series ranged from 1.61 g. to 6.38 g. 



Cm. 

 100 



90 



80 



70 



60 



50 



40 



30 



20 



10 - 



C3 



JL. 



J 



20 30 40 50 60 70 80 



Dg. total concentration 



Fig. 6. — Graph showing the influence of total concentration upon height 

 in series II. 



Height in Series II 



Figure 5 shows the height curves for the five plants of each 

 of the four groups in this series. There is clear indication that 

 the optimum phosphorus supply lies somewhere between .05 per 

 cent and .01 per cent of Qai{H.;^0^).2, the height of plant 4 being 

 greatest when all groups are considered. The difference in height 

 between plants 4 and 5 is not great in any group. The effect of 

 increasing the quantity of Ca(HoP04)„ is clearly seen in plants 

 1, 2, 3, and 4 of groups A, B, and D (pi. 8). The effect of total 



