352 Uiiivcrsitjj of CdJifnniia Publirafinitfi in A(tricit1fiiral Sciences [Vol. 1 



o])tininm tlic iiiHueuce of eoneentration on height is exhibited 

 ill a more uniform manner, as shown in plants 4 and 5 of all 

 groups (pi. 6). Plants growing in the solution of lower concen- 

 tration, in general, are taller than those growing in the solutions 

 of higher concentration. 



The influence of total concentration upon height of plant 

 when taken in connection with optimum and deficient nitrogen 

 supply is indicat(Hi in figure 2, which shows a curve for each of 

 the two measurements made on each plant, the upper curve being 

 plotted from the last measurements taken. This curve is espe- 

 cially interesting since it shows the influence of nitrogen as a 

 prime factor in growth in solutions which are of approximately 

 the same concentration. Thus in I D 4 and I B 1, where the 

 total concentrations are 3.14 g. and 3.06 g., the heights of the 

 two plants are 91.5 cm. and 5.5 cm. Such a large difference can 

 be due in this case only to the lack of nitrogen in I B 1, since 

 there is present a considerable excess of the other nutrients 

 required (pi. 7). 



A study of the early and late height curves shows that the 

 plant responded very early to the amount of salts available, as 

 is indicated by the similarity of the early curve to that based 

 upon the later measurements. The greatest final height is at- 

 tained, as was to be expected, through the continuous growth 

 of those plants which had sufficient nitrogen, while the growth 

 of tlie under-nourished plant was decidedly retarded. Thus at 

 the end of the growing season the differences in height between 

 the two groups became more marked as the time of complete 

 maturity drew near. Attention is called to this fact since it is 

 not an uncommon practice in growing plantss in water cultures 

 to harvest them before maturity. While these plants might give 

 an index of the influence of the culture solution on growth, they 

 would not give a true value for the nutritive function of the 

 solution, since increase might persist for a considerable time in 

 solutions of optimum nutritive value while plants growing in an 

 unfavorable medium would be practically at a standstill. 



