250 



MUTATIONS OF OENOTHERA SUAVEOLENS DESF. 



marks are the same in both parents. The behavior is exactly the 

 same as in the analogous crosses of Oe. biennis mut. sulfurea (Grup- 

 penweise Artbildung 1913, p. 298). The hybrids are goneoclinic 

 toward the pollen parent, or, as it is called, patroclinic. The paral- 

 lelism of the two mutants is obviously not limited to the external 

 marks, but holds good also for the hereditary qualities. It is only 

 the pollen, that decides as to the color. 



(4) Oe. suaveolens mut. lutescens 



This derivative is easily recognized in early youth by means of 

 the pale, yellowish green color of its foliage. Moreover the leaves are 

 broader and shorter than in the parent species. During the summer 

 time the difference in the color gradually decreases, but that in the 

 form increases. The stature is low, the branches spread more widely, 

 but in weak specimens the stem often remains unbranched. The 

 stems are soft, their wood does not develop sufficiently and this 

 causes many of the weaker specimens to die off before the flowering 

 period or in its beginning. The petals are as long as in the species 

 but much narrower, of an ovate shape. The fruits are thin and small, 

 with few fertile seeds. 



In the spring of 1915 I sowed sufficiently large quantities of seed 

 of the four self-fertilized specimens of my race, to determine coef- 

 ficients of mutation. The seedlings were counted in April, shortly 

 before being planted out. I found: 



Moreover I made the same determination for two seed-bearers of 

 the control experiment, mentioned above, and found among 210 

 and 420 seedlings 6 and 7 lutescens, giving percentages of 2.9 and 1.7. 

 Leaving out the extremes, we may therefore assume the coefficient 

 of mutation to be about 1 —3 percent, which is a high figure, com- 

 pared with those of Oe. Lamarckiana and other mutating species. 



In 1916 I sowed some seeds of the third generation of my race and 



