88 



PHYSIOLOGY OF NUTRITION 



These elements act like catalyzers, 1 while the plastic ash-constituents (phos- 

 phorus, sulphur, potassium, magnesium, calcium) have to do with the structure 

 of the cell and its parts; these latter may also act as catalyzers, however. 



§4. Ash-analysis of Plants.- — Besides the growing of plants in artificial 

 media, the analysis of plants grown under natural conditions is also useful in 

 the determination of the relative importance of the various mineral elements. 

 Large numbers of such analysis have been carried out, and the results obtained 

 up to 1880 have been assembled and arranged in a very helpful way by Wolff. 2 



The ash-analyses of entire plants show that the amount of each individual 

 ash-constituent is different with different plants. The agriculturist, for ex- 

 ample, recognizes three groups of cultivated forms, silicon plants, calcium plants 

 and potassium plants, according to which one of these three elements is most 

 abundant in the ash. The following table (after Liebig) contains the results 

 of ash-analyses of some of the plants belonging to these three classes. 



Salts of K and 



Na 



Silicon 

 plants 



Calcium 

 plants 



Potassium 

 plants 



f Oat straw and grain . . . 

 \ Rye straw 



Havanna tobacco 



Stems and leaves of pea 



Sugar cane 



Artichoke 



per cent. 

 34.00 

 18.65 



24-34 

 27.82 



88.80 

 84.30 



Salts of Ca and 

 Mg 



per cent. 



4.00 



16.52 



67.44 

 63-74 



12.00 

 i5-7o 



Silicic Acid 



per cent. 

 62.08 

 63.89 



S.30 

 7.81 



The total amount of ash is also known to be different in different species. 

 Water plants are richest, woody plants are among the poorest, and herbs take 

 a middle place, with reference to the amount of ash they contain. A comparison 

 of the ash-analyses of the alga Chara and the tree Fagus (beech) is shown in 

 the next table. 



Entire Ash 



Content, 

 Per Cent, of 

 Dry Weight 



Amounts of Various Elements in Ash 



Calculated as Oxides, Per Cent, of Total 



Ash 



K 2 



CaO 



MgO 



Fe 2 



2^3 



P 2 



2^5 



SO3 



SlOo 



Chara fcetida . . . 

 Fagus sylvalica 



Wood 



Bark 



Leaves 



39.080 



0-355 

 5.860 



5-i4o 



0.58 



10.00 



3 -7o 



10.50 



1 Agulhon, H., Recherches sur la presence et le role du bore chez les v6g6taux. Paris, 1910. 



* Wolff, Emil, Aschen-Analysen von landwirthshaftlichen Producten, Fabrik-abfallen und wildwach- 

 senden Pflanzen. I Theil. Berlin, 1871. Idem, Aschen-Analysen von land- and forstwirtschaftlichen 

 Producten II Theil. Berlin, 1880. 



