440 GENETICS IN RELATION TO AGRICULTURE 



which have determined the nature of these modifications and extensions 

 are very recent and they involve considerable technical knowledge of 

 biology, so that at present the progress of research in genetics is far in 

 advance of the practical application of the principles now known. How- 

 ever, some of the fundamental principles of genetics have become avail- 

 able to the practical plant breeder with the result that much unnecessary 

 waste of time and labor has been prevented and that results have become 

 more certain in some cases. 



The Future Relation of Genetics and Plant Breeding. The extent 

 to which factorial analysis has been carried in the cultivated snapdragon 

 and the garden pea is sufficient to indicate what may sometime be accom- 

 plished with plants of greater economic value. East has shown the im- 

 portance of knowing the chromosome number of a species before planning 

 extensive breeding operations, but in many of our important crop plants 

 the chromosome number has not yet been determined. The development 

 of technical plant breeding along definite genetic lines will follow the work 

 of purely scientific discovery, but it must develop more slowly because of the 

 greater length of time required and the expense entailed in the application 

 of genetic principles to crop plant improvement. However, it is not too 

 much to expect that eventually our more important crop plants at least 

 will have been subjected to such thorough germinal analysis, that the es- 

 tablishment of desired strains will become largely a matter of reference to 

 breeding records and the repetition of certain crosses and selections. 

 In other words, it is probable that the improvement of our important 

 seminally reproduced crops will have become so well systematized as to 

 make it possible to predict the outcome of crosses between recognized 

 types, as well as the behavior of new mutants. This factorial analysis 

 must apply to quantitative as well as qualitative characters. Even the 

 discovery that certain characters of economic importance are conditioned 

 by too many factors to make the production of new desired combinations 

 probable except in very extensive cultures, should prove of direct value 

 to agriculture. If the new form is sufficiently desirable the combined 

 resources of several experiment stations or other agencies might be con- 

 centrated upon its production. There must be closer coordination of 

 breeding projects for the purpose of avoiding needless duplication and 

 insuring more rapid progress. 



The Importance of Planning Breeding Operations in the Light of 

 Scientific Knowledge. It is maintained by some that two separate and 

 distinct branches of breeding should be recognized, viz., conservative 

 breeding and constructive breeding. The first is supposed to preserve 

 and utilize the desirable characters already in existence; while the second 

 attempts actually to improve the characters of plants and animals. But, 

 as Cook has shown, there is little to support the popular idea that the 



