Xo. 53S 1 



MUTATION IN (EX OTHER A 



605 



rather, all seem to agree with 0. Lamarckiana in a cer- 

 tain constellation of flower characters. From plants 

 from garden seeds, however, which have evidently un- 

 dergone crossing (e. g. y 0. suaveolens from the Xantes 

 Botanical Garden), I have occasionally obtained "mu- 

 tants" with large petals and short style-. 



It seems that the mutation phenomena in 0. La ma rcL i- 

 ana are due to a disturbed or unstable condition of the 

 germ plasm, which has probably resulted from crossing 

 in the ancestry. It is not probable, however, that the 

 retrogressive mutants, such as 0. nanella and 0. lata 

 are due to simple hybrid splitting of types which entered 

 into the ancestry. The chromosomal irregularities dur- 

 ing meiosis (maturation), which I described, furnish a 

 possible basis for the occasional appearance of retro- 

 gressive mutants in each generation. 



Certain cases, however, can not be explained as the re- 

 sult of hybrid splitting or loss of characters, and show 

 that 0. Lamarckiana has experienced a more general dis- 

 turbance of its germ plasm. Of these cases, 0. gigas 

 with its tetraploid number of chromosomes, probably 

 originated through a germinal change at another point 

 in the life cycle. A number of tetraploid species among 

 angiosperms and ferns have probably originated in an 

 analogous manner. Also 0. rubricalyx, a mutant from 



pigment predictions, "is not likely to have originated 

 through a new chromosome combination, but more prob- 

 ably through some quantitative cytoplasmic change. 



Mutation in 0. Lamarckiana, therefore, appears to be 

 a condition of germinal instability and not a simple 

 process of hybrid splitting, although this condition of 

 instability has probably been brought about through 



