198 



BREEDING CROP PLANTS 



TABLE XLV. SHELLING PERCENTAGE AS AFFECTED BY CONTINUOUS 



SELECTION 



The results presented in Table XLIV do not justify the belief 

 that selection for ear type is a means of improving yield. Other 

 experiments (Olson et al, 1918) have given results of a similar 

 nature. 



Ear -to-Row Breeding. Corn is very largely cross-pollinated, 

 therefore selection under normal conditions considers only the 

 mother plant. The ear-to-row method has been considered as 

 the quickest means of isolating an improved variety. It was 

 first introduced by Hopkins (1899) at the Illinois Experiment 

 Station. As East (1908) pointed out, the method has some 

 difficulties which have been partly obviated by improvements in 

 technic. The improvements consisted of replication; i.e., dupli- 

 cation of rows from the same ear in different parts of the field; and 

 of an attempt to overcome the harmful effects of too close in- 

 breeding. The method outlined by Williams (1905, 1907) was to 

 plant one-half the seed of each ear that was used for the ear-to- 

 row test. The remnants of those ears which excelled by the 

 progeny test were planted and the progeny intercrossed. Another 

 feature of Williams' plan was to influence several breeders to work 

 with the same, variety. New blood was then introduced into the 

 ear-to-row plot of each breeder every fourth or fifth year from a 

 grower who was using the same breeding method. The difficulties 

 of the method are that a yearly plot is needed for the ear-to-row 

 test, an isolated plot for the crossing of the remnants, a multi- 

 plication or seed plot, and the general field. Montgomery (1909) 

 suggested a plan which obviates some of these difficulties. This 

 plan is to grow an ear-to-row plot only once in several years, and 

 in the intervening years use a bulk seed plot planted by the hill 

 method, selecting only from the vigorous stalks in perfect stand 

 hills (see Chapter XIX). A review of the literature on ear-to- 



