Lutz, Triploid Mutants in Ocnothera. ;' )( S!) 



4 or more lobes, though the former were much in excess of the 

 latter. A much higher percentage lacked protoplasmic content 

 than is typical for 0. Lamarckiana. I daily self-pollinated one 

 or more flowers of 5 of the 6 1910 mutants (several were also 

 cross-pollinated) for two or three weeks during the height of 

 the flowering season (and quite often the pollen appeared suf- 

 ficiently good to insure fertilization), but only comparatively few 

 seeds were harvested at the end of the season. These were grown 

 by Dr. G. H. Shull 8 ) (from whose cultures most of the fertilizations 

 were made), in the summer of 1911. 



The question will doubtless arise in the minds of many as to 

 whether this so-called ,,mutant" 9 ) having 21 chromosomes is truly 

 a mutant or only a hybrid resulting from the accidental fertilization 

 of 0. Lamarckiana by 0. yiyas pollen, because of the chromosome 

 number and the combination of certain vegetative characters peculiar 

 to these two forms; but that it is truly a mutant and not a hybrid 

 of the latter cross is proven by the following facts: 



I. The individuals composing this group were distinguished by 

 the same chromosome number and the same vegetative characters 

 whether derived from 



a) 10 ) 0. lata (15) X 0. Lamarckiana (14), 



b) 0. Lamarckiana (14) X 0. Lamarckiana (14), or 



c) 0. lata (15) self-pollinated. 



If we suppose that this form arose in each of the above cases 

 through the accidental fertilization of the female parent by pollen 

 from 0. yiyas, we must then conclude that these plants were hybrid 

 offspring of 0. lata X 0. yiyas in Nos. 1, 2 and 6, and hybrid 

 offspring of 0. Lamarckiana X 0. yiyas in Nos. 3, 4 and 5. Hybrids 

 with 21 chromosomes do occur in each of these crosses, but so far 

 as I have observed, they do not duplicate each other in vegetative 

 character, nor have I found a 21 -chromosome hybrid in either 

 group which duplicated the vegetative characters of the 21 chro- 

 mosome mutant. 



II. Oenotltera yiyas was grown a quarter of a mile distant from 



8) Dr. Shull kindly placed his cultures at my disposal for these studies of 

 .somatic chromosome number in relation to vegetative character during each of the 

 four seasons following the beginning of the work in January, 1907. Although I 

 grew my own cultures in 1909 and 1910, the studies of the first two years were 

 made exclusively from Dr. S hull's cultures, and those of 1910, partly so. 



9) The term ,, mutant" is used throughout this paper and others to follow, in 

 the de Vresian sense, and does not necessarily imply that the offspring of the 

 plant in question will reproduce the characters of the parent throughout later 

 generations. 



10) It will be recalled that the chromosome number was determined for one 

 triploid mutant offspring from each of these groups. 



