4|li Lutx, Triploid Mutants in Oenothera. 







b) Lamarckiana hybrids which are in every way indistinguishable 

 from Lamarckiana offspring of 0. Lamarckiana X 0. Lamarckiana. 



c) Mutants. 



Cultures of 0. lata X O.yigas have been reported by de Vries(G), 

 possibly by Gates (13), and by myself (20), but no lata offspring 

 were stated to have appeared in either of the first two cultures, and 

 but 2 such hybrids have been recognized in a total of 151 offspring 

 of the above cross grown at Cold Spring Harbor in 1907, 1908 

 and 1909. The number of hybrids grown by Gates is not stated, 

 and there is considerable uncertainty as to whether he has ever 

 grown this culture; but the total reported for the Amsterdam and 

 Cold Spring Harbor cultures is over 284 28 ). It is therefore probable 

 that 0. lata appears but rarely among the offspring of this cross. 

 If the female parent of the 14-chromosome plant described in 

 Gates' first paper (7) was known to have been 0. lata, the presence 

 of 4 lata offspring in a total of 15 would indicate that these plants 

 originated as first stated; by the fertilization of 0. lata with 

 0. Lamarckiana pollen. However, we are not safe in assuming 

 that such was the case, for there are other possibilities that cannot 

 be ignored. 0. lata may have been fertilized by some other form 

 which, in union with 0. lata, may also have been capable of produc- 

 ing 0. lata offspring; furthermore, one or more of these 4 plants 

 may have arisen from the fertilization of the female parent with 

 0. lata pollen. The last however, is the least probable of the three 

 conjectures. 



These assertions are based on the assumption that each of the 

 4 plants in question were latas, as stated. But Gates has reported 

 14 chromosomes for at least one of these plants. Was this individual 

 wrongly identified, or was the chromosome number wrongly determin- 

 ed, or may 0. lata sometimes have 14 chromosomes? 



I have determined the exact somatic chromosome number in 

 28 latas. Each w r as found to have 15 chromosomes, whether mutant, 

 hybrid, offspring of mutant lata self-pollinated, or offspring of 

 hybrid lata self-pollinated; whether grown at Amsterdam, Cold 

 Spring Harbor, or the New York Botanical Garden; and whether 

 derived from de Vries cultures, from plants descended from plants 

 or seeds from de Vries, or from plants of English ancestry, in no 

 wise related to de Vries' cultures. Since all the evidence of the 

 Cold Spring Harbor studies points to the conclusion that all plants 

 having the same vegetative characters throughout their life histories 



28) As previously quoted, de Vries (0) stated that he grew 133 offspring of 

 0. lata X 0. gigas in 1907. A second lot was grown in 1908 which gave the same 

 percentages and the same characters as the first. The number of individuals composing 

 the second culture was not stated, but it is clear that the actual number reported 

 by de Vries for this cross is in excess of 133. 



