1915I DE VRIES—A MENDELIAN MUTANT 339 



From time to time I have noticed the same deviating percent- 

 ages in my own cultures. Thus, for instance, I fertilized in 1910 a 

 specimen of O. gigas by its own pollen, and among 50 seedlings 

 of its offspring 10 were dwarfs, pointing to a percentage of about 20 

 per cent/ Similar facts have since occurred more than once in my 

 cultures. 



ScHOUTEN and Gates have interpreted these figures as indicat- 

 ing a Mendehan proportion of dwarfs, and on this assumption the 

 parent plant would have been a mutant hybrid in the same sense 

 as explained above for O. brevistylis. Mutant hybrids would then 

 occur in a race which produces dwarf mutants also, and the latter 

 would then, of course, have to be considered as the products of the 

 combination in fertilization of two sexual cells, both of which had 

 mutated into nanella. The production of dwarfs from 0. gigas 

 would then follow the same process which is to be assumed for the 

 origin of 0. gigas itself from 0. Lamar ckiana; and the copulation 

 of two similarly mutated cells would then more easily be accessible 

 to experimental investigation. • 



In order to verify the exactness of this conception I have fol- 

 lowed up the progeny of such a presumed mutant hybrid, and on the 

 other hand have made crosses between 0. gigas and 0. gigas nanella. 

 In both cases the truth of the assumption was easily ascertained. 



Mutations of single gametes may be discovered by different 

 means in other instances also, the production of potential nanella 

 gametes by O. Lamarckiana being the most likely to be betrayed 

 in this way.5 I have observed such cases in crosses between 

 0. Lamarckiana and 0. rubrinervis. From these ordinarily two 

 types arise in the first generation, one of which resembles the 

 mother and the other the father. In my book on Gruppenweise 

 Arthildung I have called them "Lamarckiana" and " subrobusta." 

 Both types are usually constant after self-fertihzation. But, 

 from time to time, individuals appear which in their progeny 

 produce an unexpected number of dwarfs. The following cases 

 may be adduced. 



■» DeVries, Hugo, Gruppenweise Artbildung. p. 340. 1913. 



s Besides the production of gametes for gigas by 0. Lamarckiana, as shown by 

 the occurrence of specimens of semigigas in self-fertilized strains of the parent species, 

 or by the production of the Hero-type in crosses of 0. Lamarckiana with allied species. 



