60 PLANT BREEDING. 



HYBRIDIZING VARIETIES OF CORN. 



In the work of variety formation hybridizing is very useful. Before 

 hybridizing two varieties of corn it is best to carefully select each so 

 as to get mother plants of superior worth. Any one of several simple 

 plans may be pursued in cross-pollinating. 



First plan. — Alternate rows of each maj'^ be planted and one kind 

 detasseled, so as to insure pollination by the other. Seeds from the 

 resulting ears vnay be planted for two or three years, that the mixing 

 of blood may continue in the production of variations. From a field 

 of at least an acre of this mixed corn superior plants may then be 

 chosen for j)lanting, as indicated under the plans of selection outlined 

 above. 



Second plan. — Seeds of the choice plants of two varieties may be 

 mixed in bulk and planted in the corn nursery, one seed in a hill, as 

 above mentioned, so that mixing may occur naturally. By detasseling 

 or removing all but the best plants before flowering time, onlj^ good 

 plants will cross, and the best plants may be chosen for mother plants. 



Third 2)la,n. — Hj^brids may be made by hand pollinating, (a) choos- 

 ing superior plants? in two separate stocks in carefully planted nurse- 

 ries; (b) choosing plants in a nursery where the two varieties are 

 planted in alternate rows; (c) choosing plants in two ordinary fields, 

 either near together or far removed from each other. 



In hand pollinating, cloth bags 10 by 20 inches are used to cover the 

 ear of the plant of one variety and the tassel of the other variety to 

 be crossed. These are slipjDed on and tied a few days before the flow- 

 ers mature. The bag on the ear is removed — temporarily protecting 

 the ear from other pollen by an umbrella — and pollen from the bag 

 containing the tassel is dusted upon it. This should be repeated 

 daily for two or more days that the ear may be fully fertilized. The 

 further breeding of the mixed stocks from the hybrid ears thus pro- 

 duced may be done in a variety of ways, but in anj^ case large num- 

 bers of plants should be grown for two ot three years, that the 

 variations inaugurated by the mixture of the two races of blood 

 may have ample opportunity to go forward. These stocks may be 

 planted in the field for a few years, where a very large number of 

 plants may be used, and f i-om which in the second or third year supe- 

 rior mother plants may be chosen, that their seeds may be taken 

 into the corn nursery for further selection, as already outlined under 

 "Selecting seed corn." 



Since the nitrogen determination can now be so cheaplj^ made, it 

 would seem that the breeding of corn with heavier yield and with a 

 higher percentage of nitrogen could be made profitable on an extensive 

 scale. Nitrogen added to our corn crop would be as valuable as sugar 

 to the sugar beet. The addition of nitrogen will no doubt be much 

 slower and more difficult than the addition of sugar, but should amply 

 repay the State or private plant breeders for the expense. Careful 



