PLANT AND ANIMAL IMPROVEMENT 221 



through the utilization of hybrid vigor are no less great 

 in plants. The increased cost of seed is an item and the 

 practice can only be followed with those plants which are 

 easily crossed and which produce a large amount of seed. 

 Many plants in which production might be increased in 

 this way have such low economic value, however, that it 

 would not be profitable to utilize the method. Cases in 

 point are squashes and pumpkins. Tomatoes and cucum- 

 bers in certain crosses, on the other hand, have been 

 found to give appreciable increases in yield and other 

 desirable qualities, advantages which are readily secured 

 every time the particular cross is made. 



Maize is the plant which is most suitable for use in this 

 way, a notable fact since it is the most valuable farm 

 crop in the Western Hemisphere. The reason it merits 

 this statement is because it is easily crossed on a large 

 scale by sowing the two types to be crossed in alternate 

 rows in an isolated plot and detasseling all of one kind 

 before pollen is shed. As early as 1876 Beal ^ reported 

 that com could be increased in yield in this way. Since 

 that time numerous tests have been made and the fact is 

 established that crosses between varieties of com of some- 

 what different type may be expected to outyield either 

 parent in many cases, and when the parental varieties 

 differ in time of maturing may be expected to ripen 

 earlier than the later parent. Thus out of fifty first gen- 

 eration crosses between varieties of com grown in Con- 

 necticut, eighty-eight per cent, yielded more than the 

 average, and sixty-six per cent, yielded more than either 

 parent. The average increase in all the crosses above the 

 average of their parents was about ten per cent., includ- 

 ing the crosses which gave no indication of hybrid vigor. 



