Lutz, Triploid Mutants in Oenothcra. }v>< 



somes of birnnis maintain their individuality throughout the inter- 

 kinesis," etc. The conditions which he describes for (j n in di flora 

 (2, p. 562), Lamarckiana and gigas (4, pp. 950, 957) are much the 

 same as for biennis. He states that the individuality of the chro- 

 mosomes in O. Lamarckiana is 'generally maintained quite as clearly 

 as is indicated in Fig. 31 33'. With reference to gigas, Davis said 

 the he observed no case 'in which the chromosome boundaries 

 were no longer distinguishable, as reported by Gates'. 



In describing the interkinesis between the heterotypic and 

 homotypic mitosis of 0. grandiflora, Davis states as follows (2, p. 562): 



"The seven split chromosomes, which were at first massed 

 closely together, separate as the daughter-nucleus gradually increases 

 in size, and become distributed rather symmetrically around its 

 interior just under the nuclear membrane. A change in the form 

 of the split chromosomes becomes then at once apparent. The 

 ends of one chromosome of the pair swing away from the ends of 

 the other until they lie in approximately the same plane, when the 

 structure becomes that of two ITs joined together at the bent 

 middle regions." 



Davis also describes a similar condition for O. Lamarckiana 

 (4, p. 950). His figures for 0. biennis (3, Figs. 28 and 29), for 

 O. Lamarckiana (4, Fig. 31) and for O. giyas (4, Figs. 71 and 72) 

 illustrate his descriptions very clearly. The chromosomes are here 

 shown very loosely associated indeed, even entirely separated in 

 some cases, though still lying side by side (3, Figs. '28 and 29). 



If, therefore, the nucleus should fail to divide at the time 

 when this process ordinarily takes place, and a spindle never 

 be formed, it is quite conceivable that the tendency of these divided 

 chromosomes to complete separation might cause the halves to 

 become disassociated, independent units. If the reduction division 

 proceeding had been regular, we should have a cell resulting with 

 14 chromosomes in 0. Lamarckiana^ and 14 or 16 in O. lata according 

 to whether the 7- or 8-chromosome germ cell failed to complete 

 the second division. In case the embryo-sac was differentiated 

 from the 14-chromosome cell in O. latn, a 21 -chromosome offspring 

 could result from the union of this cell with a normally reduced 

 male germ cell having 7 chromosomes. This would explain the 

 origin of both the 21-chromosome mutants in question. 



This phenomenon, taken in connection with possible irregularities 

 of chromosome distribution in the male, could explain each of the 

 chromosome numbers of the </iyas-\ike offspring of O. hita X O.yiyas 

 previously referred to: 



$ 14 -f J 14 = 28 $ 16 -4- cf 14 = 30 



14 + 13 = 27 16 -f 13 = 29 



14 -j- 15 = 29 16 -j- 15 = 31. 



