April, 1907.] LOEW & ASO.—ON PHYSIOL. BALANCED SOLUTIONS. 71 



The theory of one of us as to the functions of lime and 

 magnesia in plants assumes the existence of calcium protein 

 compounds in the tectonic of the nucleus 1 ' and chloroplasts of 

 the higher plant forms and ascribes to magnesia the role to 

 mediate in the assimilation of phosphoric acid when nucleo- 

 proteids and lecithin are to be formed from anorganic phos- 

 phates. The theory further has pointed out that a certain 

 excess of magnesium salts will act on the lime compound in 

 the nucleus, replacing calcium by magnesium and changing 

 thereby the capacity of the nucleus for imbibition, leads to 

 disorganisation and death, while on the other hand an undue 

 excess of lime will retain the phosphoric acid and prevent the 

 formation of magnesium phosphate, of this important com- 

 pound for the assimilation of phosphoric acid. 2) 



We had never observed such intimate relations as evi- 

 dently exist between the physiological functions of lime and 

 magnesia, also to exist between potassa and magnesia. How- 

 ever recently not only a toxic action of potassium salts for 

 plants was assumed to exist but also an antitoxic action of 

 potassa to magnesia. These observations were, however, not 

 made with phenogams but only with Spirogyra and gemmae 



J > The view of some authors that lime salts are only required for certain processes 

 of metabolism in the plants cannot be upheld. It might be objected, e.g., that in this 

 case strontium salts should be capable to replace calcium salts, which is however 

 impossible; these act injuriously, in absence of lime salts. Cf. O. Loew, The Phy- 

 siological Role of Mineral Nutrients, II Edition, pp. 46 and 54 U. S. Dept of 

 Agriculture, 1903; and U. Suzuki, this Bulletin IV, No. 1. Manganese salts act 

 evidently in the same way poisonously as magnesium salts do. In accordance therewith 

 a poisonous effect for all plants from the higher algae upwards is noticed and no 

 poisonous effect for lower algse and fungi. Thus Palmella-forms and TJlothrix-like 

 filaments can grow in a b% solution of manganese sulphate, while Spirogyra is killed 

 by solutions weaker than 0.1^. 



2 > Since it was recently shown by Willstatter (Ann. Chem. 350, p. 46) that 

 the molecule of chlorophyll contains magnesium it follows that magnesium has still 

 another function to perform. Willstatter ascribes to it a r6le in the assimilation 

 of carbon. Since, however, postassa is also indispensable for the assimilation process, 

 as has been shown long ago by Nobbe, it may be possible that both these metals must 

 be present in the transformation of C0 2 into organic compounds. It deserves mention- 

 ing, that Berthelot (1906) has observed especially in the leaves, potassium compounds 

 insoluble in water. 



