332 PLANT-BREEDING 



By this means the direct observation of mutations sup- 

 ports the conclusions derived from purely comparative in- 

 vestigations. Together they teach us the great law of correl- 

 ative variability, by which one and the same internal cause 

 may affect different organs and qualities in widely divergent 

 ways. This law intimately connects the scientific results 

 and methods of selection now in use at the Swedish experi- 

 ment station at Svalof with the principles and achievements 

 of Burbank in horticultural practice and with numerous 

 other more or less isolated scientific facts and methods of 

 practice. It points out the lines for further investigation. 

 The study of correlations must be carried on on the broadest 

 possible basis. Minute and apparently small marks must 

 be analyzed and compared with valuable properties. Every- 

 where connections will be discovered. Some of them may 

 be accidental coincidences, and of no further significance, 

 but others will hold good through large numbers of instances. 

 From the broadest possible knowledge of these, new princi- 

 ples of selection will be derived, and slowly, but surely, we 

 shall approach a definite knowledge of the meaning of much 

 that is as yet hidden from our eyes. Then we shall see that 

 there is no mystery connected with the indications which 

 seedlings give concerning the fruits they will bear in later 

 years. 



