Lutz, Triploid Mutants in Oenotherii. 433 



of the chromosome number in O. yiyas says (as previously quoted) 

 L 'all the other mutants which are known have 14 chromosomes as 

 in O. Lamarckiana." 



In the next report I hope to outline the results obtained from 

 the study of somatic chromosomes in 300 Oenotheras. It is realized 

 that this number is very small, and it is not expected that all the 

 theories discussed in this report will stand or fall on the basis of 

 these limited observations; however, they are sufficient to demon- 

 strate the fact that many mutant derivatives of O. Lainarcldana 

 have a chromosome number differing from that of the parent. I 

 may anticipate a future report sufficiently to state that I have 

 found many quite distinct types of mutants with 15 chromosomes, 

 and some even with 16. There is also considerable evidence to 

 indicate that the former are produced as frequently by O. Lamarck- 

 iana as 14-chromosome mutants, and perhaps even more commonly. 



Somatic chromosome number in the Oenotheras can usually be 

 determined approximately in any form (from sections of root-tips) 

 in comparatively short time, but the exact determination of number 

 beyond all chance of error is generally a long and tedious process, 

 and such studies proceed but slowly. It is therefore hoped that 

 more workers will come into the field, and that especial attention 

 will first be given to the accurate determination of somatic chro- 

 mosome number (from sections of root-tips) in the various mutants 

 of O. Lamarckiana and other forms. Scarcely a start has yet been 

 made in this direction. 



Other subjects of present interest may be mentioned: 



1. Verification of the count of 15 chromosomes for O. lata. 



2. The determination of somatic chromosome number in the 

 various types of O. yiyas. 



3. Verification of the count of 22 chromosomes for the offspring 

 of O. lata X O. yiyas which appears to combine the characters of 

 the two parents. It is very important that the chromosome number 

 of each parent shall have first been determined. 



4. The recognition of triploid mutants, and the exact determina- 

 tion of somatic chromosome number in all such plants; a careful 

 study of the reduction process in the first and last flowers of 21- 

 chromosome mutants and hybrids. Early and late flowers from 

 the same regions of the plant should then be self-pollinated, and 

 the position of each capsule carefully recorded. Sowings from 

 each capsule should be made separately. The next step is the 

 exact determination of somatic chromosome number in as many 

 offspring as possible. 



5. An approximate estimate of the number of somatic chro- 

 mosomes in many offspring of O. Lamarckiana X O. yiyas (after 



XXXII. 28 



