212 HOW CKOPS GROW. 



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 development 

 of the plant is greatly modified by the circumstances of its 

 growth, not only in reference to its external 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 fluc- 

 tuations, (relative,) in the content of this element. The 

 percentages are arranged for each period separately, pro- 

 ceeding from the highest to the lowest: 



PERIODS. 



I. II. III. IV. V. 



Upper leaves. Lower leaves. Upper leaves. Ears. Ears. 



3.74 2.39 2.27 . 2.85 3.04 



Lower leaves. Upper leaves. Lower leaves. Upper leaves. Upper leaves. 



3.38 2.19 2.18 1.91 1.74 



Lower leaves. Ears. Ears. Lower leaves. Upper stem. 



2.15 2.06 1.85 1.63 1.56 



Middle stern. Upper stem. Upper stem. Lower leaves. 



1.52 1.34 1.60 1.43 



Upper stem. Middle stem. Middle stem. Middle stem. 



0.87 0.98 1.20 1.17 



Lower stem. Lower stem. Lower stem. Lower stem. 



0.80 0.88 0.83 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 Bretschneider and 

 Arendt is remarkably close, as appears from the figures 

 below. 



PERIODS. v 



I. II. III. IV. . V. 



Bretschneider 8.57 5.96 5.33 5.40 



Arendt 8.03 5.21 5.44 5.20 5.17 



The diminution at the 2d, increase at the 3d, and sub- 

 sequent diminution at the 4th period, are observed to run 

 parallel in both cases. 



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



