36 



PHYSIOLOGICAL ROLE OF MINERAL NUTRIENTS. 



increase in lime, while the seeds show an increase in magnesia, has 

 finally furnished a clew to the mystery of the action of these salts. A 

 number of cases will serve to illustrate that different parts of the same 

 plant contain quite different proportions of lime and magnesia. Let 

 us first consider the leaves of the Graminea% since in them the absence 

 of calcium oxalate excludes an otherwise misleading factor. The 

 following data are extracted from tables in Liebiof's work: ft 



Per cents of lime and magnesia in the ash of the grain and tin' straw <>f Graminese. 



Fart of plant. 



Grains of— 



Barley 



Oats 



Wheat 



Maize 



Rye (bran) 

 Straw of — 



Barley 



Oats 



Wheat 



Maize * 



Rye 



A better basis for a comparative estimate will be obtained if the aver- 

 age of these figures is taken and compared with the relative number of 

 molecules instead of the absolute weight. The seeds of Graminese will 

 then be found to contain for every 17 molecules of lime 100 molecules 

 of magnesia, while in the straw there will be found fully 22-1 mole- 

 cules of lime for every 100 molecules of magnesia. The leaves of 

 Phaseolus vulgaris contain in comparison to the magnesia content four 

 times as much lime as the seeds, and those of Brassica napus seven 

 times as much. The proportion of magnesia to lime in tobacco leaves 

 was found to be, on an average, as 1 to 5. The proportion of these 

 constituents in the flowers is also different from that in the leaves. 

 For example, in the case of Ihunulus litpulus there was found in 

 the— 



Flowers? 1 part magnesia to 2 parts lime. 



Leaves 1 part magnesia to 6 parts lime. 



On comparing the underground parts of the plants with the leaves, it 

 was also found that the latter contain more lime. For example, it was 

 observed in — 



Daucus carota, roots 1 part magnesia to 2.5 parts lime. 



leaves 1 part magnesia to 14.0 parts lime. 



Solatium tuberosum, tubers 1 part magnesia to 0.6 part lime. 



leaves 1 part magnesia to 6. 1 parts lime. 



"Die Chemie in ihrer Anwendung auf Agriknltur und Physiologie, 7 ed., Part I. 

 The analyses were made by Way and < >gsten, Weber, and others. 



