BUREAU OF PLANT INDUSTRY. 139 



toil of this type in connection with the military requirements of the 

 Government emphasize more than ever the importance of maintain- 

 ing an adequate supply of pure planting seed. The extension of the 

 industry to new localities brings w^ith it the danger of planting mixed 

 or inferior seed and of resulting deterioration in the quality and uni- 

 formity of the prodiict. To guard against this danger, cooperation 

 has been continued with the associated growers in the Salt River Val- 

 ley in roguing their seed- increase fields, and arrangements have been 

 made for seed selection and increase in the Impertal and San Joaquin 

 Valleys. It is desirable to make these new centers of Egyptian cotton 

 production self-contained in this respect as soon as possible. 



Selection has been continued with the Pima, Yuma, and Sakel- 

 laridis varieties, the importance of breeding work with the last men- 

 tioned, which is the principal variety grown in Egypt, having been 

 emphasized by the recent discovery of its peculiar suitability for cer- 

 tain military requirements of the Government. Hybrids have also 

 been made among the different varieties, since it has been ascertained 

 by the study of crosses between two varieties of Egyptian cotton that 

 it is possible to obtain from hybrids between distinct varieties be- 

 longing to the same general type relatively stable and uniform recom- 

 binations of the desirable qualities of both parents. In this respect, 

 crosses within the same general type are unlike hybrids between very 

 different types, such as Egyptian and Upland, since all attempts to 

 obtain stable varieties from these wider crosses have thus far been 

 unsuccessful, 



BREEDING DROUGHT-RESISTANT CROPS. 



Improved and uniform varieties of sorghum, millet, alfalfa, and 

 brome-grass especially adapted to the climatic and soil conditions 

 of the northern and north-central portions of the Great Plains have 

 been obtained by selection from mixed commercial stocks. 



IMPORTANCE OF ELIMINATING MINOR ABNORMALITIES IN CORN. 



Yields of corn are seriously reduced by the presence of abnormal 

 plants. In any field of corn will be found a large number of plants 

 that for one reason or another are practically sterile, and also many 

 plants that die before reaching maturity. These unproductive plants 

 present a large series of abnormalities, only a few of which have 

 been made the subject of study. It has been found that these abnor- 

 malities are of all degrees of conspicuousness. There is, m fact, no 

 well-marked line between normal and abnormal plants. While the 

 more conspicuous abnormalities are eliminated by ordinary breeding 

 methods, the great majority of troubles pass unnoticed, and since all 

 the difficulties thus far studied have ])roved to be recessive they are 

 carried along in hybrid condition, separating each year in a certain 

 number of plants, with the result that yields are materially reduced. 

 A method of breeding has been devised which should make possible 

 the elimination of these numerous minor difficulties, and experiments 

 have been inaugurated to test the value of this new method on a 

 commercial scale. 



SWEET CORN RESISTANT TO THE CORN EARWORM. 



An effort is being made to increase the supply of seed of the variety 

 of sweet corn resistant to the corn earworm announced in last year's 



