COMPOSITION IK SUCCESSIVE STAGES. 219 



Observe that these absolute quantities diminish in the 

 stem and leaves after the 1st or 3d period in all cases, and 

 increase very rapidly in the ear. 



Arendt found that sulphurio acid existed to a much 

 greater degree in the leaves than in the stem, throughout 

 the entire growth of the oat plant, and that after blos- 

 soming the lower stem no longer contained sulphur in the 

 form of sulphuric acid at all, though its total in the plant 

 considerably increased. It is almost certain, then, that 

 sulphuric acid originates, either partially or wholly, by 

 oxidation of sulphur or some sulphurized compound, in 

 the upper organs of the oat. 



Magnesia is translated from the lower stem into the 

 upper organs, and in the fruit, especially, it constantly in- 

 creases in quantity. 



There is no evidence that lime moves upward in the 

 plant. On the contrary, Arendt's analyses go to show 

 that in the ear during the last period of growth, it dimin- 

 ishes in quantity, being, perhaps, replaced by magnesia. 



As to potash, no transfer is fairly indicated except from 

 the ears. These contained at blossoming (period III) a 

 maximum of potash. During their subsequent growth 

 the amount of potash diminished, being probably displac- 

 ed by magnesia. 



The data furnished by Arendt's analyses, while they in- 

 dicate a transfer of matters in tlie cases just named and in 

 most of them with great certainty, do not and cannot from 

 their nature disprove the fact of other similar changes, and 

 cannot fix the real limits of the movements which they 

 point out. 



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