Sorting and blending of unit characters. 217 



the deep red stem character, the red tubercles, petal and pod characters 

 of nutans, as well as its high fertility. 



The only failure to fulfil these expectations is in the character of 

 the stem leaves which are those of nutans in all respects save the edge 

 character. The few, coarse, distant teeth over the basal half is the 

 only character by which the adult stage can be distinguished from 

 nutans unless it be that of habit. 



While all the contrast vegetative "unit"' characters possessed by 

 the two parents are transmitted, each in its entirety, to the two Fi 

 segregates, some to pycnella, the others to tortuosa, the Fi blend, 

 kyhrida nutella, inherits all, or a very large proportion of the contrast 

 characters of the two parents. In such a case it is impossible for both 

 characters of the "allelomorphic pair" to express themselves in their 

 completeness. Each is modified by the other member of the pair so 

 that an intermediate state between the two contrast characters is at- 

 tained. The "allelomorphic pairs" blend. In the rosettes, the broadness 

 and toothedness of nutans blend with the narrowness and cutness of 

 pycnocarpa; the convexity and crinkledness of nutans blend with the 

 furrowedness of pycnocarpa and the leaves are flat or nearly so. A very 

 few rosettes had leaves slightly crinkled, but they were easily distin- 

 guished from those of tortuosa. There are no real intergrading forms 

 between the three hybrids, though each one shows slight fluctuations. 

 The red color of the stems and tubercles of nutans blends with the green 

 of pycnocarpa and an intermediate state of coloration (pink) results. 

 The small bracts of nutans blend with the large ones of pycnocarpa 

 and bracts of an intermediate size appear on nutella. 



The Fl blend hybrid {nutella) presents a very interesting case of 

 sterility. When the inflorescence is covered with paper bags, or other 

 screen to prevent insects from bringing foreign pollen to the stigma, 

 no seeds are developed. Though the pods often attain a considerable 

 size and give the impression that seed is being formed, they are found 

 to be hollow, and finally die. This is not due to a failure in pollination, 

 for like the parents, and others of the smaller flowered Oenotheras, 

 pollination takes place in the bud. In the summer of 1912. when it 

 was discovered that protected flowers were not setting seed, a large 

 number were hand pollinated, using not only pollen from the same flower 

 in some cases, but cross pollinations between two individuals were also 

 made. From all these hand pollinations, only one pod developed a few 

 seeds. From these seeds two plants were raised, one of which came 



