FIFTEEN- AND SIXTEEN-CHROMOSOME OENOTHERA MUTANTS 79 
evidence to indicate that functional 8-chromosome cells of one sex 
only are produced by certain 15-chromosome individuals, and that 
these, in many forms, are female, it is possible that the functional 8-, 
perhaps even all functional 7 +-chromosome germ-cells produced by 
0. Lamar ckiana and certain 14-chromosome mutant derivatives, are 
female.20 More attention has been directed to the study of male 
than female reduction in various forms. Gates ('10, reported in 1907) 
and Davis ('11) each recorded 6-8 distributions of male heterotypic 
chromosomes in 0. Lamarckiana, but as Davis remarks (p. 952) "we 
do not know whether or not fertile pollen-grains may be formed with 
chromosomes in a greater or less number than the normal. "^^ Gates 
and Miss Thomas ('14) found the expected 7-8 distributions of he- 
terotypic chromosomes in the pollen mother cells of 0. lata; we know 
that 8-chromosome female gametes are produced by this form, yet 
we shall see that it appears that very few, if any, 8-chromosome male 
gametes, capable of functioning, are formed; nor is the presence of the 
two i6-chromosome plants in the C.S.H. culture of 0. Lamarckiana 
positive proof of the production of both male and female 8-chromosome 
germ-cells, since we do not know whether these individuals arose from 
8 + 8, or 9 + 7 unions. It is quite certain, however, that 7 -f- chro- 
mosome cells of one sex or the other, if not of both, are formed occa- 
sionally, since 15-chromosome mutants are quite common. 
We may summarize our conclusions, therefore, as follows: 
(a) I ^-chromosome mutant offspring of 14-chromosome forms are 
not invariably distinguished by the somatic characters of O. lata, O. 
semilata or IsLta-like forms. 
(b) ha.ta-like forms, and those combining certain lata characters 
with others not distinctive of O. lata, are not invariably characterized by 
IS chromosomes. 
Thus far we have considered only (a) whether when a meiotic 
irregularity in a 14-chromosome form results in the production of a 
2° This statement merely expresses a possibility and not the writer's established 
convictions. If 7 4— chromosome male gametes, capable of functioning, are never 
produced by 0. Lamarckiana, then we must concede that O. gigas de Vries arose in 
some one of the various ways suggested by Gates (and recent evidence tends to 
strengthen, rather than weaken, Gates's arguments in support of this conclusion) 
and that it was not the product of the union of two 14-chromosome gametes, as 
maintained by Stomps and Lutz. 
2^ By 0. Lamarckiana. 
