THE WHEAT CROP. 85 



tions showed us, that although the constituents of any 

 individual plant are always the same, still that there is 

 well-nigh as great a variety in the composition of different 

 plants as in that of different soils ; which at once gives 

 us a reason not the only one though why certain plants 

 thrive better on certain soils than on others. They also 

 showed us, that although the constituents of a plant 

 wheat, for instance were always the same, still their rela- 

 tive proportions might vary in different specimens or 

 varieties; and thus indicated the probability that one 

 variety might be more advantageous than another for 

 cultivation under certain conditions. In twenty specimens 

 of wheat examined (sixteen English and four foreign), a 

 variation was shown in the amount (per centage) of silica 

 assimilated of from 1*34 to 971, the one grown on calcare- 

 ous rubble, the other on a greensand loam. In phosphoric 

 acid the proportion differed from 34 '44 to 49 '22; some 

 contained 267 of potash, while in another it amounted 

 to 3 6 '6 per cent. In lime and soda a greater difference 

 was shown, the lowest proportion of lime being 115 and 

 the highest 821, and of soda '07 and 9'06 per cent. These 

 points of different proportions may have a practical value, 

 as indicating varieties of wheat more or less suitable for 

 soils of different qualities, those varieties with the least per 

 centage of phosphoric acid and potash being evidently 

 better suited for cultivation in poor soils than the others, 

 which require larger proportions of those salts for their 

 growth. 



The proportions of the organic constituents of wheat, 

 too, exhibit the same variations as the inorganic do. These, 

 however, have a far more important bearing on the value 

 of the grain, 1 and, in fact, determine its value as a feeding 

 substance, and materially influence the technical purposes 



1 Much valuable and interesting information on the influence of circum- 

 stances of growth on the composition of wheat, will be found in a paper by 



