26 MUTANTS AND HYBRIDS OF THE OENOTHERAS. 



distinctive form as to make it certain that the diseased plants were not 

 simply pathological individuals of one of the other types, but that the 

 hybrid included a strain incapable of resisting the attacks of the fungus. 

 The entire crop of seeds obtained by the cross in the previous year 

 were sown in a single seed-pan, and this strain was seen to be affected 

 even in the first foliage-leaf, while all of the others were found to be 

 wholly immune. The whole pathological effect may be said to be due 

 to the dominance of qualities of biennis. L,eaves not directly attacked 

 by fungus, on the other hand, exhibited a predominance of qualities 

 characteristic of O. lamarckiana. The variable length of the stamens 

 and pistils may, however, most reasonably be ascribed to the patho- 

 logical condition. 



A second form, No. 2.32 (PI. XVI, fig. 3), reproduces the biennis- 

 characters of the bracts, relative dimensions of the pistils, stamens, 

 and petals quite exactly, and shows only slight departures from this 

 parent in the habit of branching and form and margins of the leaves. 

 The relative measurement of the hypanthium and of the petals are 

 alike in the parents and remain the same in the hybrid. Only one 

 character seems to have been transmitted unchanged from the lamarck- 

 iana parent, while the stems are channeled something after the manner 

 of this parent, and some crinkling of the leaves is present. In this 

 instance the qualities of biennis predominates strongly in the hybrid, 

 and the qualities inherited from the other parent are of comparatively 

 minor physiological importance. It is notable, however, that the 

 general aspect of this plant is very different from that of biennis, 

 although the taxonomic analysis yields so little actual anatomical 

 divergence. This is partly due to the unusual reddish color present 

 in the leaves and stems. 



A third type, No. 2.24 (PI. XVII, fig. 5), was characterized by 

 the combination of parental qualities in such manner as to constitute 

 intermediates. The characters of the form, size, and structure of the 

 stems and leaves made a mosaic of modifications from both parents, in 

 which it would be difficult to assign greater importance to one over 

 the other. The hypanthium exhibited a length greater than that of 

 either parent, while the ovary was less pubescent than either. The 

 amount of red color present in the stems and branches was much 

 greater than that of either parent and is only duplicated among some 

 of the related species of the genus. 



The form and structure of the bracts and the crinkling of the 

 leaves were transmitted unchanged to the individual ; the size and 

 form of the petals were intermediate, and the relative length of the 

 calyx-segments and hypanthium of biennis were found. It was notable 



