310 CENOTHERA AND THE MUTATION THEORY 



by deVries, Stomps, and Bartlett that undoubted 

 wild species of (Enothera show the same kind of 

 behavior as Lamarckiana, and hke it produce 

 numerous new types. 



The next suggestion as to the cause of the un- 

 usual behavior of (Enothera came with the dis- 

 covery by Lutz that the "mutant" gigas has twice 

 as many chromosomes as has the parent form, 

 Lamarckiana (the diploid numbers being 28 and 

 14, respectively). The situation is complicated by 

 the fact that there are apparently races that look 

 like gigas but have only 14 chromosomes. These 

 two races thus closely parallel the two giant races 

 of Primula sinensis of which one is diploid and the 

 other tetraploid. The aberrant numbers observed 

 in gigas hybrids by Stomps may perhaps be due to 

 a process of fragmentation of chromosomes similar 

 to that described for O. scintillans b}^ Hance. 



Another type of variation in chromosome number 

 has been described by Gates and by Lutz. The 

 '^mutant" types lata, semilata and scintillans have 

 15 chromosomes as the diploid number, instead of 

 the 14 characteristic of Lamarckiana. As would 

 have been expected if the extra chromosome is re- 

 sponsible for their peculiarities, these forms do not 

 breed true. Each regularly produces many typical 

 Lamarckiana offspring, as well as other offspring 

 like itself. These cases have already been discussed 

 under non-disjunction (see Chapter VI). 



Although differences in chromosome number due 

 to irregularities in reduction or fertilization may be 



