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



From both table 2 and the curves in figure 2, it is evident that 

 magnesium chloride is more toxic than potassium chloride. Up to 

 the concentration of .1M, it is favorable to the growth of yeast, but 

 beyond this it becomes more and more toxic until at 1.2M concen- 

 tration there is little or no growth at all. In the case of yeast, mag- 

 nesium chloride and calcium chloride show less similarity than that 

 found by Lipman with soil bacteria, and the toxic effect of magnesium 

 chloride is nearer to that of calcium chloride than to that of potassium 

 chloride. Magnesium chloride is not so toxic to yeast as Lipman 

 found it with Bacillus sublilis. In the case of yeast, .7M concen- 

 tration of calcium chloride altogether inhibits its growth. The same 

 concentration, however, of magnesium chloride allows an appreciable 

 number of yeast cells to grow, and the same toxic effect as that of 

 .7M CaCL is not attained until a concentration of 1.2M MgCL is 

 reached. In fact, magnesium chloride stands midway between the 

 two extremes of toxicity of these four salts, namely, the more toxic 

 NaCl and CaCl 2 and the less toxic, KC1. 



Loeb, 1 ' 2 with marine organisms, found that a .5M solution of 

 magnesium chloride inhibits the development of embryos in the eggs 

 of Fundulus, and that even .125M Ca(N0 3 ) 2 is toxic. In his experi- 

 ment with soil bacteria Lipman 11 has met with about the same result. 

 He found that .4M MgCL inhibits the growth of Bacillus subtilis, 

 while for the same effect on yeast a concentration of 1.0M MgCL is 

 needed. But Magowan 10 has shown that with wheat magnesium chlor- 

 ide is the most toxic of all the four salts ; in this respect yeast resembles 

 neither the animals, nor bacteria, nor the higher plants. 



It must be noted that the magnesium chloride used in all the 

 experiments was MgCL.6ILO, as this is less hygroscopic than the 

 same salt having two molecules less of water (MgCL.4HoO), which 

 is difficult to weigh accurately. However, magnesium chloride was 

 found more toxic than potassium chloride and more favorable than 

 calcium chloride, which is directly opposite to the result obtained 

 with higher plants. 



SERIES III— CALCIUM CHLORIDE 



The experiment with calcium chloride was carried on in the same 

 way. From both table 3 and the curves in figure 3, it is evident that 

 .01 M concentration of CaCL gives the highest growth, while beyond 

 this favorable concentration CaCL is more and more toxic. In its 



