4S 



DE. E. E. GATES— CONTRIBUTION TO A 



the flowers on this plant were alike, with very little variation. These flowers would 

 not he self-fertilized in the bud because the style was too short. In the other short- 

 styled individual the styles were somewhat longer, so that in the first flowers the stigma 

 was just below the anthers, and in later flowers was touched by the anthers, as in 

 O. biennis. I have not yet determined whether these two aberrant plants resulted 

 from germinal or fluctuational variation, probably the former. 



YI. Hybridization in Oenothera. 



r 

 I 



In this section will be taken up (1) various experiments in crossing the mutants with 



■ 



each other and with 0. Jjamarckiana, and (2) the results of crossing various forms with 

 O. biennis. The race of O. biennis used in these crosses came from New York State, 

 and has abeady been described by MacDougal (1905, p. 9). Its main features are here 

 illustrated in PL 4. figs. 50-53. 



The results of these crossing experiments partly confirm DeYries's experiences in 

 crossing Oenothera forms, though there are certain contradictory results. An effort has 

 been made — particularly in the description of the hybrids between O. biennis and other 

 forms, where it is most needed on account of the brevity of DeYries's descriptions 

 of the twin hybrids — to make the description and illustration of the various forms, 

 and their relation to each other and to their parents, as clear as possible. The 

 complete description and accurate comparison of these hybrids, not merely in taxonomic 

 language, but so as to bring out the relationship of their characters, is a diflB.cult 

 task, but one which is essential to an elucidation of the laws of inheritance in these 

 forms . 



After the hybrids have been described, and the results of crosses compared with those 

 of DeYries, an attempt will be made to givear^sum^ of the various types of inheritance 

 now known to occur in Oenothera. This seems particularly necessary because the results 

 of Oenothera crosses have received little attention in the recent literature of 

 hybridization. In the last section I showed that races of Oenothera which are of hybrid 



frequently breed true, and this is in entire accord with the results of 



^.v~ 



experiments. Erom a survey of all the hereditary phenomena in the genus, it appears 

 that there are two general types of behaviour : (1) alternative inheritance; (2) blended 

 inheritance. How far these may represent fundamentally different processes will be 

 discussed after the data are presented. 



(a) Crosses involving O. Lamarckiana and its Mutants. 



DeYries made a number of crosses between O. Lamarckia/na and its mutants, with the 

 result that both parental forms appeared in the Ei, and both usually bred true in later 

 generations. I have made similar crosses, with results which corroborate those of 

 DeYries. The data from some of these crosses may now be stated. 



O. lata X O. Lamarckiana yielded in 1906 five O. lata and eight O. Lamarckiana. 

 Six of the latter, self-pollinated, produced a total of 104 plants in 1907, all of which were 

 O. Lamarckiana^ showing no difierence whatever from O. Lamarckiana of pure 



