158 HOW CROPS GROW. 



light, moisture, and soil. This is, however, as good as 

 impossible, and if we admit the wheat plant to vary in 

 form within certain limits without losing its proper char- 

 acteristics, we must admit corresponding variations in 

 composition. 



The difference between the Tuscan wheat, which is 

 cultivated exclusively for its straw, of which the Leghorn 

 hats are made, and the "pedigree wheat" of Mr. Hallett 

 {Journal Boy. Ag. Soc. Eng., Vol. 33, p. ^1i), is in 

 some respects as great as between two entirely different 

 plants. The hat wheat has a short, loose, bearded ear, 

 containing not more than a dozen small kernels, while 

 the pedigree wheat has shown beardless ears of 8f inches 

 in length, closely packed with large kernels to the num- 

 ber of 130 ! 



N"ow, the hat wheats if cultivated and propagated in 

 the same careful manner as has been done with the pedi- 

 gree wheat, would, no doubt, in time become as prolific 

 of grain as the latter, while the pedigree wheat might 

 perhaps with greater ease be made more valuable for its 

 straw than its gpain. 



We easily see then, that, as circumstances are perpet- 

 ually making new varieties, so analysis continually finds 

 diversities of composition. 



9. Of all the parts of plants, the seeds are the least lia- 

 ble to vary in composition. Two varieties or two indi- 

 viduals may differ enormously in their relative propor- 

 tions of foliage, stem, chaff, and seed ; but the seeds 

 themselves nearly agree. Thus, in the analysis of 67 

 specimens of the wheat kernel, collated by the author, 

 the extreme percentages of ash were 1.35 and 3.13. In 

 60 specimens out of the 67, the range of variation fell 

 between 1.4 and 3.3 per cent. In 43 the range was from 

 1.7 to 3.1 per cent, while the average of the whole was 

 3. 1 per cent. 



In the stems or strata of the grains, the variation is 



