IMPROVEMENT OF FIELD CROPS 1 7 



and the plant obsen^ed through youth, maturity and old age 

 before the characteristics of the individual plant are fully 

 known. The individual animals are constantly under the eye 

 of the successful breeder. The poorer animals are rejected 

 and only the better animals mated. In the case of plants there 

 is not only usually no mating, but the mature individual from 

 which the embr}'0 is obtained for the subsequent progeny is 

 unknown. This is not quite so true of maize as of the other 

 cereals, because of the method of harv^esting the crop. Even 

 if the large ear of maize is a measure of the productiveness of 

 the individual maize plant, the character of the sire is unknown. 

 In the case of the other cereals, or of potatoes, the size of the 

 grain or tuber is no necessary measure of the productiveness of 

 the parent. A small grain from a fine, well-bred individual is 

 better than a large grain from a poor, indifferently-bred indi- 

 vidual. Other things equal, a small tuber from a la/ge hill of 

 potatoes is better than a large tuber from a small hill. In case 

 the large and small seeds come from equally good heads of 

 wheat, which will probably be the case under average con- 

 vlitions, the large seeds may perhaps give the best results, 

 fiispecially as under field conditions the larger size may be of 

 jidvantage in enabling the plant to get a more vigorous start. 

 Specific proof of this is, however, lacking. Hays believes it to 

 be established that the best heads of wheat, as well as best 

 plants, should be selected. In the case of maize the butt and 

 tip grains have been found to be substantially equal to the 

 middle grains of the ear. (272) To succeed in plant breeding 

 the seed must be selected from individuals which possess the 

 characteristics it is desired to perpetuate. 



36. Examples of Improvement or Modification in Plants. — 

 Many of the modifications w^hich have taken place in plants 

 during cultivation by man may be said to be unconscious. At 

 least there was no definite plan to accomplish the results 

 attained. 



