62 



LECTURE IV. 



Herapath analysed five varieties which are indicated by the letters in 

 the table. 



Further, although we may assume that quite similar indi- 

 viduals of the same species growing in the same soil and 

 under the same external conditions would yield an ash of 

 approximately the same composition, yet the fact that the 

 individuals vary in the vigour of their development leads to 

 considerable differences in the composition of the ash. This 

 is shewn by the accompanying table of analyses of plants of 

 Brassica oleracea made by Pierre. 



