No. 518] GENETIC AL STUDIES ON OENOTHERA 111 



darker green than those of grandiflora, but broader, 

 thinner, and a lighter green than those of muricata. 



On reaching maturity four plants exhibited flowers al- 

 most as large as those of grandiflora, and a habit and 

 foliage more like this parent than was shown by the other 

 hybrids; these four plants were, however, only 1.2 m. 

 high while neighboring grandifloras were 1.5 m. high and 

 much more extensively branched. The remaining hy- 

 brids, twenty-five in number, were strikingly muricata- 

 like in habit and foliage except that the leaves were 

 broader than those of that parent and the flowers more 

 than twice as large, in size somewhat midway between 

 the small flowers of muricata and the very large flowers 

 of grandiflora. These hybrids then, as in the case of the 

 muricata X gigas, fell into two groups (twin hybrids) 

 with marked resemblances to one or the other of the 

 parents, but with all structural characters blended. The 

 proportion of four g ran di flora-like to twenty-five muri- 

 cata-\ike forms probably does not represent the normal 

 ratio between the plants of these two groups which would 

 be expected to appear in about equal numbers. 



There was certainly no evidence from the cultures of 

 any tendency on the part of the hybrids to resemble 

 markedly the male parents (patroclinous) as was re- 

 ported by De Vries ('07) to be the rule among (Enothera 

 hybrids of the Onagra group. On the contrary five sixths 

 of the hybrids were strikingly similar to the female 

 parent, although, as stated above, it is not likely that 

 these proportions represent normal ratios. 



4. biennis X grandiflora. The parents of this cross 

 were carefully selected with an end in view. The biennis 

 plant was found wild at Woods Hole and transferred to 

 the garden of 1908; it was chosen as represent;! five of 

 the broader-leaved types of this variable specie ^'ith. 

 however, only medium-sized flowers. This strain of 

 biennis has proved constant in the cultures of 1909, pre- 

 senting the characteristic biennis habit of a main stem 

 about 1 m. high and long side branches arising from near 

 the base of the plant. The grandiflora parent was one 

 of nine plants grown from seed collected by S. M. Tracy 



