270 



TWIN HYBRIDS OF OENOTHERA HOOKERI T. AND G. 



Total average 46 percent, or almost the same figure as in the two 

 previous tables. Evidently there is no difference between the male 

 and the female gametes of the laeta. And since both parents of the 

 cross are themselves isogamic, there is no reason to expect a different 

 behavior for their hybrids. 



If our premises are right, we must get the same results when we 

 replace the velutina in these crosses by the pure species. I made 

 these combinations in the same year along with the others and 

 counted the hybrids in the same manner. I got the following results: 



Table 4 



Oe. grandifloraxOe. Hooker i. 

 Crosses of laeta with Oe. Hookeri. 



Cross 



Oe. (gr. x H.) laeta x Hookeri 

 Oe. (H. x gr.) laeta x Hookeri 



Oe. Hookeri x Oe. (gr. x H.) laeta 

 Oe. Hookeri xOe. (H.xgr.) laeta 



Total 



69 

 71 



72 

 71 



velutina 



46 

 53 



57 

 47 



Percent 

 velutina 



67 

 74 



79 

 66 



Mean 



70.5 



72.5 



This table confirms the results of the previous one, since the 

 reciprocal crosses give about the same figures. The percentages 

 for velutina are higher than in the crosses between laeta and velutina, 

 but they seem to indicate the same process of splitting. 



Our conclusion is, that the laeta hybrids of the reciprocal crosses 

 of Oe. grandiflora and Oe. Hookeri, and all of them, split their male 

 and female gametes into about equal groups of potential laeta and 

 potential velutina and that the combination of these in fecundation 

 produces about one-half of constant velutina and one-half of laeta, 

 which repeat the splitting in the succeeding generations. 



During the course of my investigations into the hybrids of Oe. 

 Lamarckiana I have often observed that the size of the flowers is 

 a character which is more or less independent of the other marks. 

 So it is in this case also. In the first generation all the plants have 

 large flowers, intermediate between those of the parents. In the 

 second, however, much diversity is seen, on the beds of laeta as well 

 as on those of velutina. Small-flowered specimens with flowers no 

 larger than those of Oe. biennis appear and even some intermediate 

 sizes may be found. For a closer study I chose the four groups of 

 velutina, mentioned above, on account of their uniformity in all 

 other marks, and counted their flowering specimens. 



