58 



PHYSIOLOGICAL ROLE OF MINERAL NUTRIENTS. 



Thus far few authors have expressed any view as to the primary 

 functions of magnesia. Raumer observed that Phaseolus multtjlorus, 

 grown in culture solutions without magnesia, reached 1 meter in height, 

 after which the internodes no longer lengthened, but thickened abnor- 

 mally. The new leaves also remained small and ceased to produce 

 chlorophyll — an interesting case of chlorosis, which disease may be 

 produced by other causes than by the absence of iron, as has been 

 already pointed out. Raumer ascribed to magnesia and not to lime, 

 as Boehm has done, the transportation of starch, basing his claim on 

 the ground that in the beginning the leaves contain not only consider- 

 able starch, but also a relatively large proportion of magnesia, a 

 condition found later also in the stems. Finally, magnesia is found 

 to be increased in the seeds, in Avhich starch also is generally deposited. 

 This hypothesis does not, however, seem to be well founded, since the 

 relations indicated are not direct ones. Many other facts make it 

 much more probable that it is the proteids and not the starch that have 

 a close relation to magnesia. Where development is going on, starch 

 is required for furnishing the necessary carbon and hydrogen in 

 the production of proteids. Here magnesia is connected with the 

 protein production and not with the migration of starch. . Further- 

 more, the organoids of starch formation, the plastids, also require 

 ^magnesium salts for their growth and multiplication, since they con- 

 tain phosphoric acid in their nucleo-proteids; hence there also exist 

 some reasons for the belief in the remote connections between the 

 starch content of an organ and the amount of magnesia present. 



INCREASE OF MAGNESIA IN OILY SEEDS. 



If the writer's theory as regards the relation of magnesia to phos- 

 phoric acid is correct, more magnesia ought to be found where both 

 compounds, nucleoproteids as well as lecithin, are formed than where 

 nucleoproteids alone exist, since the assimilation of phosphoric acid is 

 required not only for the formation of nucleoproteids, such as chroma- 

 tin and plastin, but also for that of lecithin. Lecithin is a constant 

 concomitant of fat, and therefore seeds rich in fat ought to contain, 

 cet. par., more magnesia than such as are rich in starch. A review of 

 Wolff's ash tables confirms this deduction. For 1,000 parts of organ- 

 ized substance there are of magnesia in — 



Starchy seeds. 



Oily seeds. 



Oats 



Parts. 

 1.9 

 2.0 

 2.0 

 1.9 



Cotton 



Flax 



Paris. 

 5.G 

 4.7 

 4.9 

 4.6 



Barley . . 

 Rve 











Pnpe 





