208 HOW CROPS GROW. 



among others, the following results {Vs. Si., IV, 

 p. 59) : 



Of 100 parts of the following fixed ingredients of clover, 

 were dissolved in the sap, and not dissolved— 



These researches demonstrate that potassium and sodi- 

 um — bodies, all of whose commonly-occurring compounds, 

 silicates excepted, are readily soluble in water — enter into 

 insoluble combinations in the plant ; while phosphoric 

 acid, which forms insoluble salts with calcium, magnesi- 

 um, and iron, is freely soluble in connection with these 

 base? In the sap. 



It should be added that sulphates may be absent from 

 the plant or some parts of it, although they are found in 

 the ashes. Thus, Arendt discovered no sulphates in the 

 lower joints of the stem of oats after blossom, though in 

 the upper leaves, at the same period, sulphuric oxide 

 (SOs) formed nearly 7% of the sum of the fixed ingre- 

 dients. {Wachsthum der Haferpf., p. 157.) Ulbricht 

 found that sulphates were totally absent from the lower 

 leaves and stems of red clover, at a time when they were 

 present in the upper leaves and blossom. ( Vs. St. , IV. , p. 

 30 TabzUe. ) Both Arendt and Ulbricht observed that sul- 

 phur existed in all parts of the plants they experimented 

 upon ; in the parts just specified, it was, however, no 

 longer combined to oxygen, but had, doubtless, become 

 an integral part of some albuminoid or other complex or- 

 ganic body. Thus the oat stem, at the period above cited, 

 contained a quantity of sulphur, which, had it been con- 

 vei'ted into sulphuric oxide, would have amounted to 14% 



