28 MUTANTS AND HYBRIDS OF THE OENOTHERAS. 



The leaves of all rosettes of the hybrid showed laminae variously 

 crinkled, caused by the unequal growth of the mesophyllary and fibro- 

 vascular tracts of the laminae, a character which is well marked and 

 constant in O. lamarckiana, but which was not seen in 0. biennis in 

 any of the cultures, although it has been seen in a few wild specimens 

 which were growing luxuriantly. Furthermore, the crinkling of the 

 leaves was exhibited in the stem-leaves of the entire hybrid. In one 

 type, that illustrated by 2.27 and consisting of two individuals, a 

 further lack of correlation in the growth of the tissues of the leaf was 

 exhibited, which consisted in an excess growth of the midrib over 

 that of the wings of the laminae, giving it an upward convexity which 

 might easily be converted into the reverse form. This was present in 

 both the rosette and stem -leaves. 



The forms of leaves were so diversely intermediate that it is not pos- 

 sible to point to any important dominancies in this respect, except such 

 as are found in the types of terminal rosettes exhibited by stems and 

 branches. One, a regular, flattened, and symmetrical rosette, charac- 

 teristic of lamarckiana, was dominant in all individuals except those 

 of 2.24, which bore tufted rosettes in the five individuals included 

 with it. 



The branching habit of O. biennis, by which secondary members 

 were borne on all parts of the main axis, decreasing in length upwardly, 

 showed exactly the complementary prevalency, being present in all 

 individuals with terminal rosettes- of the pattern of O. lamarckiana. 

 Type No. 2.24, which bore biennis rosettes, gave off large basal 

 branches, and the upper part of the main axis was more densely 

 branched than in 0. lamarckiana, so that the habit of the pistil-parent 

 in this particular was not exhibited in pure form by any member of 

 the hybrid. 



Stems of rounded cross-section were found to be more prevalent 

 than those with deep channeling, the latter occurring on only five indi- 

 viduals of the hybrid. 



The capacity for self-fertilization as indicated by the relative 

 length of the stamens and pistil was dominant in all types, except that 

 of 2.1, or in about 29 out of the 33 individuals examined. A sharp 

 separation with regard to this character may be detected in securing 

 pure fertilizations. In order to obtain capsules with pure seeds it is 

 but necessary to inclose the inflorescences of 0. biennis in the parch- 

 ment bags and the pollen will fall on the stigmatic surfaces without 

 the intervention of any agency whatever except gravity. On the other 

 hand, 0. lamarckiana rarely sets seeds unless pollen is transferred to 

 the stigmas by insects or by hand, although in the open air the same 

 purpose is sometimes accomplished by the wind. 



