352 Colchicine 



been developed then or not, a proof that dioecious races in phmts 

 could be established as ]3olyploids would certainly have been re- 

 ported when it was, in 1938.'^'' 



As early as 1925 the similarity in ploidy between animals and 

 dioecious plants was obscr\ed.''-^ Both cases were generally dijiloid. 

 Among many plants jjolyploidy was a mode of sjiecies formation. 

 These were not dioecious. Therefore, an explanation for the lack of 

 polyploidy in animals and in dioecious plants seemed to be related 

 to the diploid state. When a polyploid species of Empetru^n hennapli- 

 r<Hlituin was found to be hermaphroditic, the fact was particularly 

 interesting because there was a related diploid species, dioecious 

 Empetniin )iignim.'''' Conflicting evidence accumulated when a dioeci- 

 ous tetraploid strain of J'aUisneria was reported. Briefly this was the 

 state of affairs when Westergaard decided to test the hypothesis by 

 making tetraploids from diploid dioecious species of MeUnidriiun. He 

 began the project in spite of the fact that no well developed methods 

 for making polyploids were available at that time. Colchicine had not 

 been announced. i*^'' ^''' '*-^ 



In America, polyploidy and sex determination in plants were 

 started because colchicine should quickly lead to the evidence needed 

 to test the question raised by Muller about sex determination as 

 limited to diploidy in animals and dioecious plants.'' The projects 

 in Denmark and America were started about the same time and first 

 results from each came close together.-^^ Yet there was no a\vareness 

 that either was studying the same problem. 



Soon other work began in japan,-^*^- '^^ and there were additional 

 studies in America. •^■■' A large volimie could be compiled from this 

 problem after only a few years of investigation. Some excellent work 

 was done and colchicine provided enough breeding material to demon- 

 strate conclusively that sex determination was not limited to a dip- 

 loid state when plants were under consideration. Howe\er. male 

 and female plants are not strictly comparable to maleness and female- 

 ness among animals. In plants there are three kinds, with respect to 

 production of flowers: (1) plants producing staminate, or pollen- 

 bearing, flowers, (2) some giving ]jisiillate, or seed-producing, flowers, 

 and (3) plants that have staminate and pistillate structures in the 

 same flower. These are called male, female, and hermaphroditic, re- 

 spectively.'''' 



Adopting the sex-determining code used for animals, notably 

 DrosophiJa, diploids are XX as females and X}' for males; in addition 

 there are other chromosomes called autosomes. A tetraploid female 

 carries the chromosomes XXXX and male XX)T with a tetraploid 

 set of autosomes designated AA. At once, it can be seen that another 

 combination XXX)' may exist at the tetraploid level. If further 



