54 PHYSIOLOGICAL ROLE OF MINERAL NUTRIENTS. 



upon a higher differentiation of the chloroplasts. The beautiful chlo 

 roplasts of Spvrogyra show a high degree of differentiation, the pyre- 

 noids in the chloroplasts being the manufacturers of the starch. 



It is true Schnritz also observed well-defined chloroplasts multiplying 

 by bipartition in such simple alga forms as Protococom, Stichococcus, 

 and Palmetto,, but these chloroplasts appear to be of a lower order than 

 those of Cladophora, Zygnema, or Spirogyra. 



The nutrition of the chloroplasts is in all probability cared for by the 

 nucleus; hence it is reasonable to suppose that nuclei which prepare 

 calcium-protein compounds for themselves furnish these same com- 

 pounds to the chloroplasts also. This is probably the simplest expla- 

 nation as to why chloroplasts become sensitive to even neutral oxalates 

 in all plants the nuclei of which are killed by oxalates. Where the 

 nuclei contain calcium-protein compounds the chloroplasts also contain 

 them. 



The writer has advanced the view that a higher development in form 

 and function becomes possible only when the lower forms of life 

 acquire the ability to assimilate lime and to utilize the resulting calcium- 

 proteid compound for the construction of the nucleus. This seems to 

 him the simplest explanation of the fact that lime salts are required 

 by all plants except the very lowest forms. Agreeing especially well 

 with this view is the further observation that neither neutral oxalates, 

 nor magnesium, nor strontium salts are injurious to these lowest 

 forms." although noxious to all other plant life. 



If lime were necessary only for certain processes of metabolism in 

 plants, as some authors claim, it would not only follow that the higher 

 forms of algae have quite a different mode of metabolism from the 

 lower ones, but it would also remain entirely incomprehensible why 

 magnesium salts act so poisonously on the nucleus and why only cal- 

 cium salts can prevent this deleterious effect. It would be Aery inter- 

 esting to know the exact line of organisms below which calcium salts 

 are not required and above which they are indispensable for plant 

 life. A division of the alga' into two such groups would certainly 

 prove instructive. 



POSSIBLE RELATIONS BETWEEN LIME AM) THE TRANSPORTATION OF 



STARCH. 



One of the first disturbances to appear when there is a deficiency of 

 lime is the cessation of starch transportation. Starch gradually accu- 

 mulates in the lower parts of the stem, and even its transportation 

 from the storage receptacles to tin 1 axial parts may gradually stop. It 



" l'lilnicUa can develop quite well, even in 4 per cent solutions of neutral potassium 

 oxalate or magnesium sulphate to which traces of ammonium sulphate and potassium 

 phosphate had been added. Beer yeast may be kept for several hours at 30° C. in a 

 1 per cent solution of magnesium nitrate without serious injury. 



