Special Functions and Relations 175 



94. The role of magnesium. Magnesium is an ele- 

 ment concerning some of the functions of which practically 

 all physiologists seem to be agreed. It may be inferred 

 that it does not play a direct role in the formation of pro- 

 teins. It is, in general, more toxic to protoplasm than the 

 other mineral nutrients, and according to Loew its chief 

 function is probably to be found in the conveyance of 

 phosphoric acid for assimilation. Magnesium is more 

 abundant in those parts of the plant undergoing develop- 

 ment, as in growing tips and seeds. This would imply 

 that it acts indirectly to condition the formation of the 

 nucleo-proteins. Loew believes that "the same amount 

 of base can serve over and over again as the vehicle for 

 assimilation of phosphoric acid." It is well known that 

 magnesium is migratory in the plant, so that maturing 

 organs are considerably depleted. Attention has been 

 called to the fact that oily seeds contain a larger proportion 

 of this element than do starchy seeds, and this is regarded 

 as a point strengthening the argument of Loew respecting 

 the function of this element, especially since lecithin is 

 formed in cells rich in oil. Reed has also found that there 

 is some definite connection between magnesium and phos- 

 phorus. He has demonstrated that oil globules are not 

 formed in Vaucheria when magnesium is lacking in the 

 nutrient solution, and he believes that there is an intimate 

 relationship between magnesium and vegetable oils. 



95. The role of calcium. The judicious use of lime 

 in plant production may be the determining factor in the 

 active fertility of a soil. It appears that the addition 

 of lime to soils is a practice which has shown more or 

 less alternation in various agricultural epochs. Wheeler 



