MUTANTS AND HYBRIDS OF THE OENOTHERAS. 9 



ONAGRA (OENOTHERA) BIENNIS (I,.) SCOP. 



Many collectors and taxonomists include a number of elementary 

 species in Onagra biennis and attribute to it an extremely wide range 

 of fluctuating variability. On the other hand, workers who have 

 carried on cultural experiments with individuals representing a typical 

 elementary species describe it as fluctuating between very narrow limits. 

 The actual inclusion of the species is not so important, in connection 

 with the present investigation, as the degree of constancy of the various 

 strains grouped around the species and sometimes included in it. 



In order to carry on observations on these points, and upon " the 

 changes produced by cultivation," upon which some systematists lay 

 so much stress, a number of plants of 0. biennis (in the strictest sense), 

 growing in uncultivated land in the New York Botanical Garden in 

 1903, were selected to form the basis of a pedigree-culture in 1904. 

 Seeds were duly harvested at the end of the season and sown in the 

 propagating house early in January. The plantlets were transferred 

 to the experimental grounds late in May and began to bloom early in 

 July. The species was thus grown as an annual during a season of 

 about nine months in soil rich with fertilizers. Furthermore, the 

 individuals were placed in rows, over a meter apart, and were kept free 

 from the competition of weeds. Briefly stated, it may be said that in 

 no single feature, nor in any instance, did these plants transgress the 

 measurements, or show different forms of organs, from those of wild 

 specimens in the vicinity. The size of the leaves, the amount of the 

 pubescence, the size of the flowers and capsules, and the formation of 

 the branches are capable of modification by soil-moisture, humidity, 

 intensity of illumination, and competition, as in thousands of other 

 well-defined species, but these modifications did not bring the species 

 nearer in aggregate character to any of the closely allied forms. Exact 

 records and observations were kept during the entire life-histories of 

 the individuals, by the aid of which the following description has 

 been prepared : 



Seedling about two months old. Leaves nearly glabrous ; blades 

 oval to oblong-oval, the larger ones about 10 mm. wide, obtuse at the 

 apex, each rather gradually narrowed into a petiole (fig. i) . 



Seedling five months old. Rosette open ; leaves rather copiously 

 fine-pubescent; blades oblong to elliptic, the larger ones fully 2.5 cm. 

 wide, quite approximately repand-denticulate, with the teeth more 

 pronounced at the base, acute at the apex, each narrowed into a short 

 petiole. (PL III, fig. i.) 



Mature rosette. Leaves ample, rather copiously fine-pubescent, 

 the larger ones about 27 cm. long, 6 to 7 cm. wide ; blades oblong to 



