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 coérdination 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 
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