22 THE PLANT WORLD. 



student of "Genetics", as Professor Bateson aptly calls the 

 new science which has the pedigree-method as its peculiar 

 instrument, has limited his attention to the study of "pure- 

 line" cultures and it is recognized by all such students that 

 the usefulness of the pedigree-method has not been ex- 

 hausted until every possible combination has been made with 

 the material in hand. Thus, in the case of the most gigantic 

 piece of pedigree-culture work that has yet been done, name- 

 ly, the studies upon the Oenotheras by de Vries, followed on 

 a large scale by MacDougal and many others, there is abun- 

 dant published data showing the result of crossing each of the 

 several mutants with their parent and with each other. It 

 may be granted that the cause of science will be advanced by 

 the repetition of some of this work for the sake of confirma- 

 tion or of further analysis, but the points to be made here 

 are that these combinations have been made and that the 

 making of such combinations is a prominent feature of all 

 pedigree-culture studies that have been made or are being 

 made. It is needless to urge that in nature no other than the 

 possible combinations exist, and that therefore when with 

 respect to any species or group the full scope of the pedigree- 

 method has been utilized we have the fundamental data upon 

 which alone can be based any proper conception of what goes 

 on in nature, and that the data so found when properly con- 

 firmed by repetition are applicable to all nature in which the 

 particular species or group in question is involved. 



The pedigree-method with the resultant perfect knowl- 

 edge of ancestry has given to biological science the two most 

 illuminating suggestions which have come to it from any 

 source in many years, namely Mendelian inheritance, and 

 the Mutation theory, with their common postulate, the exist- 

 ence of unit-characters and character-bearing units or deter- 

 minants. It is not known how universal these great truths 

 are but evidence is accumulating daily to show that they are 

 truly of wide-spread and fundamental value. The only test 

 of the extent of their applicability is the one by which they 

 were discovered, namely, the pedigree-method. 



