Volume 1 1 Number 2 



The Plant World 



FEBRUARY, 1908 



THE PEDIGREE-CULTURE: ITS AIMS AND 



METHODS. 



By Dr. George Harrison Shull. 



There is a considerable body of data now on record of 

 every degree of accuracy and inaccuracy, upon which it is 

 easy to base discussions of variation, heredity, evokition and 

 kindred topics if one has a good imagination and a sufficient 

 faith in the correctness of data he may wish to cite, and the 

 eternal verity of certain hypotheses which were put forward 

 by some ancient seer, or which hang like a cloud on the hori- 

 zon of his own inner consciousness. The experimentalist lacks 

 this sublime faith. His motto is "Ignoramus, in hoc signo 

 laboremiis." Investigation shows him that the available 

 data are scanty indeed that are not written all over with 

 question-marks, which would need to be exchanged for excla- 

 mation-points in order to justify the strenuous attitude taken 

 by some writers who seem to assume that these momentous 

 questions are either already settled or are beyond the legiti- 

 mate sphere of experimentation. 



From some of these contemners of experimentation 

 comes the criticism that the distinctive feature of the pedigree- 

 culture method is isolation unlike anything which commonly 

 occurs in nature, and that the results can ha\'e valid applica- 

 tion only to those rare situations in which similar isolation is 

 found in nature. This statement of the case is quite erro- 

 neous and may prove misleading to those not familiar with 

 the scope of the pedigree-method. The distinctive feature of 

 the pedigree-culture method is not isolation, but perfect 

 knowledge of ancestry to a certain number of terms. No 



