4|(l Lutz, Triploid Mutants iu Oenothera. 



If anthers of 0. lata are carefully examined with a hand lens 

 it will usually be found that they have not opened and exposed 

 such pollen as has been produced. By teasing them open with 

 needles, it will be seen that they are partially filled with dry, shriveled 

 grains lacking protoplasmic content. Scattered through this mass 

 one can usually find a few grains which appear normal and healthy. 

 If the number is increased to any considerable extent, the swelling 

 of the large grains forces the anthers open in normal fashion, and 

 the pollen is then exposed. Sometimes an anther is thus opened 

 throughout its entire length, and sometimes only at the place where 

 the bunch of normal pollen has been produced. One can not there- 

 fore say, no matter how barren the anthers of a plant may appear 

 upon occasional examination, that it does not, very rarely, produce 

 a tiny bit of pollen. Since a 21 -chromosome mutant appeared in 

 a Cold Spring Harbor culture of 0. fata self-pollinated, having 

 vegetative characters resembling 0. Lamarckiana in certain respects 

 and 0. gigas in others, and a 22-chromosome mutant having vegetative 

 characters strongly suggesting intermediacy between 0. lata and 

 0. gigas appeared in another culture of 0. lata self-pollinated, it is 

 not impossible that one or more of the plants of Gates' culture 

 derived from the open pollination of 0. lata and assumed to be 

 offspring of lata X () - .(/?//, were mutant offspring of 0. lata 

 fertilized with (). lata pollen. 



If the 0. lata parent of the 21-chromosome plant referred to 

 in "Chromosomes of Oenothera" (10) was grown in the vicinity of 

 0. Lamarckiana, for example, there would be no more occasion for 

 assuming that this plant was derived from the fertilization of 

 0. lata by (). gigas pollen than by 0. Lamarckiana pollen, for a 

 mutant is now known to have arisen from 0. lata X O- Lamar- 

 ckiana having 21 -chromosomes and many vegetative characters sug- 

 gestive of 0. gigas. 



While it is therefore possible, and quite probable that the 20- 

 and 21-chromosome plants of unknown male parentage originated 

 through the fertilization of the 0. lata parent by 0. gigas, as assumed 

 by Gates, there is no means of proving it, either from the evidence 

 of chromosome number or vegetative character; nor can we with 

 any more security assume that they are mutants. 



In his paper on "The Chromosomes of Oenothera" (10) Gates 

 states, as previously quoted, that another plant in this cross which 

 was believed to have been pure O. lata X 0. Lamarckiana, but 

 which appeared to have all the characters of 0. gigas, was found 

 to have 21 chromosomes. Since the 20-chromosome plant derived 

 from the unguarded seed-package w r as then encorporated in his 

 report (13) upon the offspring of O. lata X O. gigas, the reader is 

 left to wonder whether the 21-chromosome plant was not similarly 



