OENOTHERA RUBRINERVIS, A HALF MUTANT. 



In the spring of 1913 in a culture of Oenothera rubrinervis I noticed 

 some young plants, the leaves of which were a little broader than 

 those of the other rosettes. Although the difference was very small, 

 I planted them separately and saw that the deviation did not in 

 crease until the time of flowering. The spikes, however, gave proof 

 that the aberrant specimens constituted a type of their own, since 

 the bracts repeated the marks of the primordial leaves, being broader 

 and more flattened than in ordinary rubrinervis. There were 7 speci- 

 mens of the new form among a culture of 25 plants, all of which 

 flowered in August. This indicates a percentage of about 30. In the 

 following year the seeds of the new form gave a uniform progeny, 

 whereas those of the normal specimens repeated the splitting. 

 Thereupon I studied their seeds and found that about one-fourth 

 of those of 0. rubrinervis were empty, but almost every seed of the 

 new type contained a living embryo. On account of this very small 

 but constant difference the new form was designated as mut. dese- 

 rens 1 ). Evidently it might have escaped observation in previous years, 

 the individuals simply being taken for weaker specimens of the type. 

 1 studied the progeny of as many self-fertilized specimens of 0. 

 rubrinervis as were available, therefore, and found the new type 

 among all of them, and as a rule in correspondingly high numbers. 

 Different strains of rubrinervis yielded the same result. 



If we should apply the principle of Bartlett concerning mass 

 mutation, and that of Morgan concerning lethal factors to this case, 

 as I have made use of them in explaining the secondary mutability 

 of 0. grandiflora and 0. Lamar cki ana 2 ), we would conclude that 0. 

 deserens is a mass mutation of 0. rubrinervis, and as such is a repe- 

 tition of the initial mutation which produced the 0. rubrinervis 

 from 0. Lamarckiana in my garden. This initial mutation must have 

 occurred in a sexual cell, which, after copulation with a normal 



Zeitschr. f. Ind. Abst. 16 : 262. 1916. Opera VII, p. 131. 

 2) Mass mutation and twin hybrids of Oenothera grandiflora Ait. Bot. Gaz. 

 65 : 377-422. 1918. Opera VII p. 201. 



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