Lutz, Triploid Mutants in Oenothcra. 4K> 



in which I was interested at the time. During the height of the 

 season, from the first of July until the first of September, these 

 plants were the subject of almost constant daily observation from 

 4, 5 and 6 A. M. until twilight. Somatic chromosome numbers 

 have been carefully studied in 61 of these hybrids (including the 

 first 3 grown in 1907), accurately determined in 52 of the lot, and 

 approximately in the remaining 9. 



The results obtained from the three plants of the first cross 

 were reported (18) in August, 1907. 40 of the second cross were 

 studied, and although, as stated in a short note 24 ) given out in 

 February, 1909 (20), the number was not exactly determined in all, 

 the following numbers were reported to have been found among 

 these hybrids: 15, 22, 23, "plants having yiyas number of chromo- 

 somes (30 in each case so far definitely counted)", "and some possibly 

 21". 18 individuals have since been added from the second cross 

 (some of which consisted of bud fixations only), making a total for 

 the two cultures as stated (1907, 3; 1908, 40 -f- 18). 



The chromosomes of the hybrids of the third culture were not 

 examined. 



Not only has the count of 21 been clearly ascertained for 

 certain hybrids of this cross since the publication of the first note, 

 but it has been found that this is one of the two most common 

 numbers. However, I have never observed a 21 -chromosome plant 

 among offspring of O. lota X O. yiyas having characters which 

 'appeared to be intermediate between 0. lata and 0. yiyas' as stated 

 by Gates. In each of the 1(5 hybrids in which I have found 

 21 chromosomes the characters of the pollen parent appeared to 

 have been combined with those of 0. LamarcMana, commonly, and 

 with those of 0. nibri-Hcm's and other forms occasionally; 

 various types of the pollen parent doubtless entering into these 

 combinations. Although but 9 of the 16 came to flower (6 as 

 annuals, 3 as biennials), the rosettes of the remaining 7 show T ed no 

 sign of lata character that was recognized. 



Also, hybrids do occur in this cross with characters inter- 



24) When this note was published it was the intention to follow soon after 

 with a detailed description of this culture; but upon attempting to prepare the 

 report it became apparent that no logical explanation of many of the curious combina- 

 tions of chromosome number and vegetative characters found in these hybrids could 

 be offered on the basis of our almost complete ignorance of the normal behavior 

 of 0. lata when self-pollinated or crossed with another of its kind, and our limited 

 knowledge of the range of variation of chromosome number among the different 

 types of 0. gigas. Publication has therefore been long withheld until the cultures 

 referred to could be grown and studied. The work has now been carried sufficiently 

 far to explain most of the points of interest among the offspring of 0. lata X 0- 

 gigas and they may therefore be again referred to in this report. Full, detailed 

 descriptions will follow in a later publication. 



