34 



OENOTHERA GIGAS NANELLA, A MENDELIAN MUTANT. 



The first two seed-bearers had evidently about one-half of their 

 egg cells mutated into nanella, which by the fertilization with the 

 pollen of dwarfs must, all of them, become nanella specimens. The 

 two last-named plants, although externally not differing from the 

 others, had only very few mutated sexual cells, and therefore pro- 

 duced only about 3 per cent of dwarfs. 



The experiment showed at the same time that hybrids between 

 0. gigas and 0. gigas nanella have the features and the stature of the 

 former type, and thereby justified the assumption made above in 

 the explanation of the behavior of mutant hybrids. 



I made the reciprocal cross in the same year, fertilizing some 

 dwarfs of my race by the pollen of normal plants of 0. gigas. The 

 fecundation was a difficult one and I got only 38 seedlings, all of 

 which developed into tall plants of the stature and character of 

 0. gigas (1914). 



In order to study the segregation of dwarfs in the next genera- 

 tion I fecundated a number of specimens of the three described 

 groups of artificial hybrids and sowed their seed in 1915. On the 

 basis of Mendel's law the expectation is, for all of them, 25 per cent 

 dwarfs, or somewhat smaller numbers on account of the lesser 

 viability of these dwarfs. The sowings of 1915, counted in May 

 and June, gave the results shown in table VI. 



Table VI. 

 Dwarfs in the second generation of 0. gigas x 0. gigas mut. nanella. 



These figures give sufficient proof that the crosses between 0. gigas 

 and its dwarfs follow the law of Mendel. 



