COMPOSITION IK SUCCESSIVE STAGES. 



231 



are due, in part, to the fact that Arendt analyzed only 

 large and perfect plants. Bretschneider, on the other 

 hand, examined all the plants of a given plot, large and 

 small, perfect and injured. The differences illustrate 

 what has been already insisted on, viz., that the develop- 

 ment of the plant is greatly modified by the circum- 

 stances of its growth, not only in reference to its exter- 

 nal figure, but also as regards its chemical composition. 



The relative distribution of nitrogen in the parts of the 

 plant at the end of the several periods is exhibited by the 

 following table, simple inspection of which shows the 

 fluctuations (relative) in the content of this element. The 

 percentages are arranged for each period separately, pro- 

 ceeding from the highest to the lowest : 



PEBI0D3. 



I. 



Upper leaves. 



3.74: 



Lower leaves. 



3.38 

 Lower leaves. 



2.15 



II. 

 Lower leaves. 



2.39 

 Upper leaves. 



2.19 



Ears. 



2.06 

 Middle stem. 



J.62 

 Upper stem. 



0.87 

 Lower stem. 



0.80 



I III. 



lUpper leaves. 



I 2.27 



Lower leaves. 



2.18 



Ears. 



1.86 



Upper stem. 



1.34 

 Middle stem. 



0.98 



Lower stem. 



0.88 



rv. 



Ears. 



2.85 

 Upper leaves. 



1.91 

 Lower leaves. 



1.C2 

 Upper stem. 



1.60 

 Middle stem. 



1.20 

 Lower stem. 



0.83 



V. 



Ears. 



3.04 

 Upper leaves. 



1.74 

 Upper stem. 



1.56 

 Lower leaves. 



1.43 

 Middle stem. 



1.17 

 Lower stem. 



0.79 



5. Ash. — The agreement of the percentages of ash in 

 the entire plant, in corresponding periods of the growth, 

 of the oat, in the independent examinations of Bret- 

 schneider and Arendt, is remarkably close, as appears 



As regards the several parts of the plant, it was found 

 by Arendt that, of the stem, tlie upper portion was richest 

 in ash tliroughout the whole period of growth. Of the 

 leaves, on the contrary, the lower contained most fixed 

 matters. In the ear there occurred a continual decrease 



