12 MUTATIONS, VARIATIONS, AND RELATIONSHIPS OF THE OENOTHERAS. 



OENOTHERA BREVISTYLIS. 



A culture was made from seed harvested by De Vries in Amsterdam in 1 899 

 and said by him to contain about 25 per cent brevistylis, the seed being the 

 product of the first generation of a cross between 0. lamarckiana and O. 

 brevistylis. Twenty-one plantlets appeared and were inspected, and some 

 seemed to form rosettes with much more rounded and abruptly pointed apices 

 than O. lamarckiana. This was the only distinction that could be made 

 between the parental type and the derivative, during what would naturally 

 be the first year of development. In addition one example of 0. nanella as a 

 mutant from the parental type was included. With the beginning of the 

 formation of lengthened internodcs in the stem but little difference between 

 the plants was discernible until flower-buds appeared. At that time the 

 leaves on the terminal portions of the branches and the bracts seemed rela- 

 tively much broader, and the flower-buds might be distinguished at some 

 distance by the fact that they were more cylindrical than the parental type, 

 and were .abruptly short-pointed. An examination of the structure of the 

 flower revealed the fact that the style is much shorter than in 0. lamarckiana 

 and that the stigma generally appears in the throat of the flower and some- 

 times is not to be seen without tearing the hypanthium apart. 



It has been noted by De Vries that the length of the style varies widely 

 (as much as i cm.), and in this is offered an example confirmatory of results 

 communicated by the authors in a recent paper (MacDougal, Vail, Shull & 

 Small, 1905), in which the mutant characters were found to offer a wider 

 amplitude of variability than the correspondent characters of the parental 

 type. In addition to the above general characters, it is to be noted that, as a 

 consequence of the extreme shortness of the style, pollination fails in many 

 cases and comparatively few capsules are matured. 



The evidence offered by this plant is of the greatest interest in connection 

 with questions concerning the survival of mutants in the habitat of the paren- 

 tal form, especially in view of the intemperate indulgence which many authors 

 show in theoretical discussions upon questions of this character. 



O. brevistylis was discovered August 20, 1886, by De Vries, as represented 

 by 2 individuals. Despite the greatest care and the most rigid inspection it 

 has never been observed to arise in any of the cultures in Amsterdam or New 

 York, and the supposition is certainly allowable that it is no longer included 

 among the mutants given off by the parental type. The characteristic qual- 

 ities of O. brevistylis are recessive when hybridized with 0. lamarckiana, and 

 consequently the first generation resembles 0. lamarckiana in outward form 

 but carries O. brevistylis, which reappears in the next or the second generation 

 of the hybrid, forming on an average one-fourth of the progeny, according to 

 the simple Mendelian formula. O. brevistylis is a retrogressive departure from 



