PARENT AND OFFSPRING 385 



distinct spines upon the surface, but the number of spines 

 varies. The form and surface of one hundred seeds were 

 studied. The table below shows the variation found in the 

 number of spines in these seeds: 



Number of spines 1,2,3,4, 5, 6, 7, 8,9 



Number of times occurring 1, 3, 7, 9, 25, 37, 25, 12, 1 



The plant known as " Spanish needles " has conspicuous 

 yellow ray flowers. The number of the ray flowers varies, 

 though this variation is often unnoticed. A count of three 

 hundred and fifteen heads of this plant was made, and the 

 following table resulted: 



Number of ray flowers 3, 4, 5, 6, 7, 8, 9, 10, 11 



Number of times occurring 2, 3, 8, 16, 52, 221, 9, 0, 1 



It is not only the form or the number of parts that varies 

 but the chemical composition also. In connection with at- 

 tempts to grow the best types of corn for the different needs 

 of agriculture and other industries, careful studies were made 

 to determine the percentage of oil and of protein substances 

 in corn. It was found that in some of the ears the percentage 

 of protein was as high as 12.54 per cent, while in others it 

 was as low as 8.96 per cent. The oil content also ranged 

 from 5.39 per cent to 4.03 per cent. 



397. Hybrids. One of the best breeds of cattle for the 

 beef -producing sections of the United States is the Hereford 

 (fig. 178). In some parts of the country Herefords and other 

 breeds of cattle have been seriously affected by a disease 

 carried by the cattle tick, and the cattle industry has suffered 

 greatly from this cause. The zebu, or Brahman bull, of India 

 (fig. 179) is immune to the tick and is thus free from the 

 disease which the tick carries. The zebu is not ordinarily 

 regarded as being as good for beef production as our native 

 cattle, It occurred to certain cattle growers to produce cattle 

 by interbreeding Herefords and zebus, in the hope that the 



