MUTANTS AND HYBRIDS OF THE OENOTHERAS. 1 5 



undulate, obtuse or merely acutish at the apex, each rather gradually 

 narrowed into a petiole. (PL X, fig. 6.) 



Seedlings five months old. Rosettes not dense ; leaves glabrous or 

 nearly so, except the ciliate margins; blades spatulate, some of them 

 narrowly so, the larger ones 2 to 2.5 cm. wide, shallowly repand-dentic- 

 ulate, mostly acute, as long as the petioles or longer. (PI. Ill, fig. 2.) 



Mature rosette. Leaves conspicuously elongated, obscurely fine- 

 pubescent, the larger ones about 26 cm. long, 25 to 30 mm. wide; 

 blades narrowly spatulate, repand-dentate, more distantly so and with 

 prominent teeth near the base, petioles relatively slender. 



All of the forms included in, and arising from, O. cruciata are 

 capable of self-fertilization when the inflorescences are inclosed in 

 bags. So far as present information goes the species of the evening- 

 primroses native to northeastern America may be said to have compar- 

 atively small flowers and to be capable of self-fertilization, although' 

 visited frequently by flying insects. The species ranging to the south- 

 ward have larger flowers, and by reason of the superior length of the 

 pistils are adapted to cross-fertilization, although it is not definitely 

 known that self-fertilization does not ensue. In O. argillicola the early 

 protrusion of the stigmatic surfaces from the unopened flower-bud 

 has the appearance of a positive adaptation for securing pollen from 

 other flowers, by the agency of wind, gravity, or insects. 



HYBRIDS. 



Among the crosses made in the New York Botanical Garden 

 during 1903, that of 0. lamarckiana X O. cruciata and the reciprocal 

 were attempted. The first only was successful, as the castration of 

 the flowers of O. cruciata was not accomplished sufficiently early to 

 prevent self-fertilization. Likewise the removal of the stamens of 

 0. lamarckiana was not done in such manner as to exclude the action 

 of its own pollen and the pistil-parent appeared as a pure strain in the 

 cultures. 



0. lamarckiana X O. cruciata. A detailed study of the hybrids 

 obtained by the pollination of O. lamarckiana by O. cruciata was made 

 by De Vries, but the pollen-parent was evidently a highly variable 

 hybrid race which bore the general vegetative characters of the 

 true cruciata, but which showed a fluctuating variability in its flowers, 

 from an atavistic, obcordate form of petal to others of the slender 

 cruciata type. The form in question is known in Europe as Oeno- 

 thera cruciata varia and is held by De Vries to be probably a hybrid of 

 O. muricata and cruciata. (De Vries, 1903, pp. 100-110, 593-633.) 



