\')\ Lutz, Triploicl ]\Iutants in OenotJtera. 



frequency with which unreduced male germ cells are produced in 

 O. lata. On the assumption that this phenomenon occurs much 

 more rarely in the male than in the female germ cells, we could 

 not draw conclusions from the study of 2.5 or 30 plants, should 

 29-chromosome hybrids not be found among this number of in- 

 dividuals. 



In 1908 I covered the stigmas of a number of flowers of 0. 

 giyas with pollen from 0. lata. The seed-capsules filled out nicely, 

 and I anticipated a good harvest, but they were found in the 

 autumn to contain only flat seed; - seed-coats without contents. 

 The cause of this peculiar occurrence is unknown. The pollen of 

 the lata used in this cross successfully fertilized its own flowers 

 and several of 0. Lamarckiana. Furthermore, the yiyas of the cross 

 produced well rounded seeds when pollinated by 0. yiyas. I may 

 add that all my attempts to fertilize 0. yiyas with 0. nanella and 

 0. Lamarckiana in 1908 and 1909 resulted similarly. It is hoped 

 that someone will again attempt to fertilize O. yiyas with 0. lata. 



The union of an unreduced female germ cell with a normally 

 reduced male germ cell will therefore explain the 21-chromosome 

 offspring 0. Lamarckiana X 0. Lamarckiana, and the 22-chromo- 

 some offspring 0. lata self-pollinated; but how shall we account 

 for the 21-chromosome offspring of 0. lata self -pollinated, and 

 0. lata X 0. Lamarcltianat 



These can be very simply explained by the irregularities of 

 chromosome distribution observed in male germ cells. If one 

 chromosome occasionally passes to the wrong pole of the spindle 

 at the reduction division, it is possible that 0. lata may produce 

 pollen with 6 and 9 chromosomes respectively, and 0. Lamarckiana 

 pollen with 6 and 8 chromosomes respectively. The union of 15- 

 and 6-chromosome germ cells might then be expected to produce 

 offspring with 21-chromosomes. 



There is no evidence to tell us at present whether a germ 

 cell having a reduced number of chromosomes which is less than 

 the normally reduced number for 0. Lamarckiana may unite in 

 fertilization with another germ cell. But it will be shown in the 

 following report that there is much evidence to indicate that 

 offspring never result from the union of two germ cells whose combined 

 number of chromosomes is less than the diploid )utntbcr for 0. Lamarck- 

 inna. It is conceivable however, that offspring might result from 

 a combination which restored the missing chromosomes (6 -f- 8 or 

 8 -\- 6). However, we have no positive proof as yet that offspring 

 are ever produced from the union of two germ cells in one of 

 which the reduced number of chromosomes is less than the normally 

 reduced number for 0. Lamarckiana. Therefore, until we have 



