316 ESSENTIALS OF BOTANY 



time of planting one seed its descendants might be made 

 to cover more than 5,000,000 acres of wheat-fields. 



Wheat-breeding is still making such rapid progress that 

 it is not now possible to say how much the quality and 

 quantity of our wheat crop may yet be improved by the 

 introduction of better varieties. The total number of 

 acres in the United States differs considerably from year 

 to year. It seems likely, as a rule, to exceed 45,000,000 

 acres. The average yield ranges between ten and fifteen 

 bushels per acre, although it is possible with the most 

 improved seed on the best soils to raise more than forty 

 bushels per acre. Choice of the best seed would undoubt- 

 edly increase the average yield to from thirteen to eighteen 

 bushels. It is easy to see how important a gain this would 

 be, even if the price of wheat were no more than seventy 

 cents per bushel. 



395. Hybridizing. — Hybridizing, as the term is now 

 generally used, means the production of seed by the action 

 of pollen of one variety or species on the pistil of another 

 variety or species. Nearly always both species must at 

 least belong to the same genus in order to produce seed 

 that will grow, and often different species of the same 

 genus cannot be made to hybridize so as to secure good 

 seed. The offspring produced by hybridization are known 

 as hybrids. 



It has long been known that hybrid plants are often 

 extraordinarily variable, but the law which governs their 

 characteristics (in many though not in nearly all cases) 

 was not discovered until 1865.^ 



Recently much use has been made of hybridizing in 

 order fo set plants to varying, and the most desirable 



1 See Bailey's Plant Breeding, Cliaijtcr IV, The Maenilllau Company. 



