150 University of California Publications in Agricultural Sciences [Vol.3 



amount absorbed varies but little from that of the control. In the 

 roots magnesium is present in large amount when growth is low in 

 culture 2, but in succeeding cultures the percentage found falls off 

 sharply and remains abnormally low without any relation to growth 

 or concentration of the solution. The percentage of iron is high in 

 cultures 6 and 7, in which the weight of the plants was small. 



Substituting magnesium chloride in equivalent concentration for 

 the calcium chloride used in the preceding series, the results are of a 

 very different order from those in table 15. The absolute growth of 

 the tops is greater than in series 14. Root growth does not parallel 

 the growth of the tops. The toxicity of the solution is scarcely evident 

 at some concentrations while markedly increased at others. Absorp- 

 tion, with the exception of the magnesium in the roots, is usually low, 

 amounting to about that of the control, but the percentages of calcium 

 and magnesium found bear no apparent relation to the differences in 

 growth. Iron, however, shows the inverse relation already noted in 

 many other series with calcium and magnesium, that is, high percent- 

 age present when growth is low, and vice versa. The toxic and antag- 

 onistic effects as well may be due in this instance to the ferric ion, but 

 this statement is by no means indisputable. 



In several tables following, the effects of copper salts are given. 

 Previously copper salts have been shown to be highly toxic to plants 

 as well as to a wide variety of vegetative forms. That they may also 

 be stimulating has been shown recently by Forbes 28 using solution 

 cultures, and by Lipman and Gericke 29 in soil cultures. The reader is 

 referred to the latter paper for an extensive review of the subject. 



The results with copper chloride are reported in table 16. Growth, 

 especially that of the roots, was limited in every concentration re- 

 ported. In fact, the growth of the roots was so limited that their 

 weights are not given. There is a suggestion of antagonistic action 

 between the nutrient solution and copper chloride in cultures 3 and 5. 

 The percentage of magnesium found is high where growth is low. 

 The same is not true of calcium, the percentage of which is low and 

 decreases as growth decreases to a certain extent. A trace of copper 

 was found in every case and appreciable amounts had penetrated 

 the plant tissue at the two higher concentrations. When ferric 

 chloride is added together with copper chloride marked antagonism is 

 shown. Table 17 will make this effect evident. In this series, as in 



28 Univ. Calif. Publ. Agr. Sci., vol. 1 (1917), p. 395. 

 20 Ibid., p. 495. 



