114 FIELD CROPS 



stroying them. The work of these birds and rodents may 

 be checked to a considerable extent by treating the seed corn 

 with tar. The corn is put in a kettle slightly warmed and 

 moistened; then tar is applied and the corn stirred, just 

 enough being used to make a very thin film of tar about 

 each kernel. A tablespoonful should be sufficient to treat 6 

 or 8 quarts of seed corn. After the kernels are coated with 

 tar, planting is facilitated by applying road dust, ashes, or 

 air-slaked lime, so that the kernels will not stick together. 



IMPROVEMENT OF CORN 



152. Problems in Improvement. There are many prob- 

 lems connected with the improvement of seed corn which 

 are not met in the improvement of some of the other farm 

 crops. The chief difficulty involved in improving corn 

 comes from the fact that it is . open-fertilized ; that is, the 

 female flowers of one plant are naturally fertilized by pollen 

 from the male flowers of other plants. On this account 

 selected strains are very likely to become mixed with poorer 

 individuals, and the work of selection may in this way be 

 entirely lost or its effect greatly reduced. Wiile progress 

 is made by the selection of the best ears of corn, the ear 

 indicates only the character of the mother plant on which 

 it grew and nothing of the character of the male plant 

 or plants that produced the pollen to fertilize its kernels. 

 Both parent plants must be taken into consideration. 



153. The Ear~to-Row Method. The fact that appear- 

 ance does not always enable one to select the ears that will 

 give the largest yields has long l^een recognized. Many 

 years ago corn breeders adopted the practice of planting the 

 seed from the selected ears in separate rows side by side in a 

 uniform field, so that their comparative jdelding power could 

 be determined. Such ear-to-row tests almost always indicate 

 a very wide variation in the yielding power, even though 

 such ears may be similar in appearance. It is not at all 



