COBB AND BARTLETT: INHERITANCE IN OENOTHERA 469 



also has a very distinctive habit that would enable it to be equated 

 with the corresponding flat-leaved form. Its lower stem leaves, 

 and the leaves of branches that do not bear inflorescences, are 

 very narrowly linear, and exceedingly small. The leaves and 

 leaf-like bracts of the upper portion of the stem, and of the in- 

 florescence-bearing branches, are two or three times as broad, 

 and much longer, giving an effect to the plants as though the 

 flowering branches were all bud-sports on a plant of an entirely 

 different sort. The dimorphic foliage of mut. setacea is well 

 represented in a former paper (see footnote 2). F. dimorpha has 

 exactly the same characteristic, the leaves being flat instead of 

 revolute, but showing the same well-marked dimorphism. Never- 

 theless, after having equated mut. formosa with f. typica, mut. 

 alhicans{}) with f. grisea, and mut. setacea with f. dimorpha, 

 there are still difficulties in the way of classifying the flat-leaved 

 hybrid progeny. Each form shows far more variation than is 

 customarily encountered in an Oenothera progeny. 



In mut. formosa there is considerable variation in the develop- 

 ment of the leaf blade, in addition to the revoluteness. If a 

 leaf were flattened out, if would not be as broad as a correspond- 

 ing leaf of f. typica. Moreover it would show a markedly ir- 

 regular development of tissue. The flattening that takes place 

 as a result of hybridization with strain C leaves the weaker 

 plants with irregularly developed blades, although the stronger 

 plants are in every respect fine f. typica. The variation with re- 

 gard to blade development within each distinguishable form 

 renders the cultures difficult to classify. Some of the plants that 

 must be referred to f. typica, and that prove to act like f. typica 

 in heredity, are much smaller and weaker than is commonly the 

 case. It is generally when the plants are young that the imper- 

 fect development of leaf blades is obvious. As a plant becomes 

 older, the leaves of the new growth are successively more and 

 more normal, until at length it will pass a cursory examination 

 as typical in every way. The smaller and weaker plants often 

 bear branches as strong and robust as those of the best-developed 

 typica. In a number of cases these branches have been so strik- 



