THE ASSOCIATION OF CHARACTERS 289 



rious comparison of the figures in the tables. It is almost 

 superfluous to mention that the collections are largely 

 illustrated by drawings and photographs, and that charts 

 giving the results of the tables in a statistical way facilitate 

 the work. Pedigrees have been drawn for most of the 

 important novelties of the station. 



The work of Dr. Xilsson and his staff at the Swedish 

 agricultural experiment station at Svalof is a model of the 

 combination of science and practice. The problems it has 

 to solve are purely practical ones, but the method depends 

 upon exact scientific studies. The station is a private 

 enterprise, founded by the Swedish agriculturists for their 

 own direct use; it has neither to serve educational aims, 

 nor to yield results of theoretical significance. No purely 

 scientific researches are carried on, no grouping of results 

 with the sole object of contributing toward the solution of 

 biological problems is allowed. But its experience has 

 taught the indispensableness of scientific principles and 

 methods. Only under their guidance may the practical 

 work be kept within limits which guard it against useless 

 and superfluous experiments, and which cause it to attain 

 its purpose by the shortest and most direct way. This 

 method of applying science to practice has opened previously 

 unsuspected possibilities and .discovered new fields of in- 

 vestigation in the study of the highly interesting relations 

 between botanical marks and qualities of practical value. 

 It will soon bear fruit for the doctrine of evolution and for 

 the theory of specific units in addition to its conspicuous 

 results for agricultural practice. 



D. CORRELATIONS IN FLUCTUATING VARIABILITY 



Correlation is the name given to regular coincidences of 

 apparently independent characters and marks. This reg- 

 ularity is not meant to be absolute; it simply means the more 



