372 



OENOTHERA RUBRINERVIS, A HALF MUTANT. 



produce the empty grains. If we compare this formula with the 

 results of the crosses described in my book (pp. 266—267), we find 

 a complete harmony, as I shall now try to show. 



Fertilized by 0. Lamarckiana and analogous mutants, 0. oblonga 

 must give (obl.+velu.)x(Lam.+velu.)=obl.xLam.+obl.xvelu.+ 

 velu.xLam.+velu.xvelu.=25 per cent empty grains +25 per cent 

 oblonga +25 per cent Lamarckiana +25 per cent empty grains. The 

 expectation is therefore for two types and these in equal proportions. 

 The two types always appeared and no others besides them, but 

 the percentage figures are very variable. I found them as follows: 



The reciprocal crosses cannot produce any oblonga, since this is 

 assumed to be suppressed in the pollen. The only exception is 0. 

 scintillans, which gives rise to a high amount of oblonga after self- 

 fertilization, and therefore may produce the same mutant after a 

 cross. I found as follows: 



The pollen of 0. oblonga must produce, after crosses with different 

 species, only velutina, as is easily seen from our formula. No oblonga 

 and no laeta are to be expected. 0. biennis, 0. syrticola, 0. Cocker elli, 

 and 0. Hookeri fecundated with 0. oblonga uniformly gave this 

 result. The reciprocal crosses, however, must give a splitting, the 

 laeta hybrids assuming the characters of 0. oblonga. The percentages 



