286 Colchicine 



of selection between diploid and aniphiploid is one of degree and 

 speed rather than absolute difference. Genetic types can be isolated 

 more quickly in diploids than in polyploids if one can base his evi- 

 dence on a specific character and extend the idea to a whole set of 

 characters.* Selection as a result of interspecific segregation creates a 

 good opportunity for making wholly new lines."" 



Regardless of the plant, whether diploid or tetraploid, the testing 

 methods are important to success in measuring the gains made, in 

 keeping the good qualities, and in raising the standards if possible. 

 In tetraploid rye the testing side by side of diploid and tetraploid 

 is inijjossible, and consequently an adjustment must be made by a 

 yield factor with another plant.^i This at once complicates evaluation 

 of the polyploid against the diploid. There are many other prob- 

 lems of testing peculiar to certain plants, and tetraploids are involved 

 because the success of the polyploid may depend upon the mode of 

 testing rather than the qualities of the polyploid itsell. 



The list of principles is not comj^lete in the above survey, but 

 a start has been made. More information is needed before the ad- 

 ditional principles of polyploidy breeding can be described in gieater 

 detail. 



11.6: The Scope of Research 



Colchicine increased the frequency of induced polyploids beyond 

 that possible with any other method known up to 1937. This dis- 

 covery had two major effects upon research in the plant sciences all 

 over the world. (1) Polyploidy, already a subject of study, was in- 

 creased immediately. (2) New programs were started because greater 

 reliability could be placed upon this technique and much time could 

 be saved in converting the diploids into polyploids. The net result 

 of these two developments has been an unusually great expansion in 

 research with polyploidy in many nations.^^- ^^ In fact, a detailed re- 

 view of all work with colchicine goes beyond the jjermissible allot- 

 ment of space in this review. 



One might single out specific cases where certain scientists have 

 had an exceptional influence upon jjolyploidy and greater than aver- 

 age progress has been made accordingly. For example, the personal 

 interest that Vavilov took in polyploidy led to great activity in cyto- 

 genetics in Russia.'" In Sweden, Nihlsson-Ehle made special efforts 

 to organize laboratories such as the chromosome laboratory at Svalof 

 and other institutes in that country.^" These and other special in- 

 stitutes^-' tluoughout the world were at work on problems in poly- 

 ploidy before colchicine became known as a tool for creating poly- 



*See Reference Xo. 10 -i in C^haplei 12. 



