GROWTH OF TURNIPS. 35 



eleven parts of food absorbed by the plants, nine parts 

 went to the leaves and only two parts to the roots. 



We find a very different proportion in the third 

 stage ; for during twenty 'days the weight of the leaves 

 has increased by 6,507 pounds, that of the roots by 

 11,638 pounds, which gives a daily increase of 



Leaves. Eoots. 



325 pounds. | 582 pounds. 



During this third stage the plants take up daily some- 

 what more than double the amount of food taken up on 

 any given day of the second stage, and this increase 

 must stand in proportion to the daily enlargement of 

 the surface of the roots and leaves ; but the food 

 absorbed is distributed in the plant in a very different 

 manner. Of twenty-five parts by weight of food ab- 

 sorbed .and assimilated, nine parts only remain in the 

 leaves, the other sixteen parts serve to increase the mass 

 of roots. 



In exactly the same ratio as the leaves approached 

 the limits of their developement, they lost the power of 

 applying to their further growth the food which they 

 had absorbed, and which now transformed into organ- 

 isable matter was deposited in the roots. The same 

 nutritive particles which went to form leaves, so long 

 as the mass of foliage kept on increasing, now became 

 constituent portions of the root. 



This migration of the constituents of the leaves and 

 transformation into constituents of the root appear to be 

 most clearly shown in the fourth stage. The total 

 weight of leaves, which on the 1st September still 

 amounted to 19,200 pounds, had by the 5th October, 

 or within the space of thirty-five days, decreased by 

 7,992 pounds, that is 228 pounds a day ; in other 

 words, out of every thirty-four leaves ten had withered, 

 while the roots had increased by 22,392 pounds, or 640 

 pounds a day a daily increase much more considerable 

 than during the third stage. 



It is evident that with the advance of autumn, with 

 the lower temperature and diminished action of .sun- 



