CHAPTER IX 



TRIPLOIDS 



IN recent work a number of threefold, or triploid, 

 types have also been recorded. Some of these trip- 

 loids have arisen from known diploid types ; others 

 have been found in cultivated plants, while still others 

 have been found in the wild state. 



Gates and Anne Lutz described triploid plants of 

 Oenothera (scmi-gigas), with 21 chromosomes. Triploids 

 of Oenothera have since been described by de Vries, van 

 Overeem, and others. They are supposed to be produced 

 by the union of a diploid with a haploid germ-cell. 



The distribution of the chromosomes of triploids dur- 

 ing maturation has been studied by Gates and Geerts and 

 van Overeem. They find that while, in some cases, the 

 chromosomes are rather regularly distributed at reduc- 

 tion, in other cases some of the chromosomes are lost and 

 degenerate. Miss Lutz found in fact great variation in the 

 kind of offspring produced by triploids. Gates records 

 that, in one 21-chromosome plant, the two cells resulting 

 from the first maturation division contained "almost in- 

 variably" 10 and 11 chromosomes respectively and only 

 occasionally 9 and 12. Geerts found more numerous ir- 

 regularities. He describes 7 of the chromosomes going 

 regularly to each pole, while the remaining 7 that were 

 unpaired were irregularly distributed to the poles. This 

 account fits well with the view that 7 conjugate with 7, 

 leaving the remaining 7 without partners. Van Overeem 

 states that in Oenothera, when the triploid serves as the 

 mother plant, the results show that most of the ovules are 



