OENOTHERA LAMARCKIANA MUT. VELUTINA. 



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the visible changes in the external structure. The same loss accom- 

 panies the mutation into gigas, rubrinervis, and some newer mutants, 

 but does not occur in such cases as those of 0. lata, 0. scintillans, 

 0. cana, and others (see Opera VII, p. 83). 



I made a series of crosses in order to study the nature of this 

 latent mutation of 0. blandina. They led to the discovery of some 

 points which seem to deserve a more thorough study than I could 

 give them until now. 



In the first place, it is to be expected that in crosses with those 

 species which do not produce such empty seeds the high figures of 

 both parents will simply be repeated. I tried these cases, deter- 

 mining the amount of normally developed germs in lots of 200 seeds 

 each, after the method already described. I made the crosses in 

 1914 and 1915, and in most cases in both the reciprocal directions. 

 The seeds were taken from 5 successive fruits, and carefully pre- 

 pared so as not to lose any small grains. The results are given in 

 table I. 



Table I 



* The dash ( — ) means that the cross has not been tried. 



In some instances I cultivated the first generation of the hybrids 

 in 1915 and tried their seeds after self-fertilization. I got almost 

 the same figures: 0. blandina x Chicago 86 per cent, 0. Hookeri x 

 blandina 97 per cent, and 0. syrticola x blandina 93 per cent. 



In trials with other species the hereditary property of 0. Lamarck- 

 iana of making germs in only one-half of its seeds is recessive to 

 the normal condition of producing almost only normal grains. It 

 behaves in the same way in crosses with 0. blandina. The results 

 are given in table II. 



Of course it is to be expected that those mutants which them- 

 selves give high percentages after self-fertilization will do the same 

 in their crosses with the velutina mutant (table III). 



The crosses were made in 1915. 0. rubrineris is the same strain 

 as used in my Gruppenweise Artbildung. 0. erythrina is a new mutant 



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