FIFTEEN- AND SIXTEEN-CHROMOSOME OENOTHERA MUTANTS 9 1 
parent in each case are transmitted to the offspring through the 8- 
chromosome garnetes. In cases with which we are famihar, the 8- 
chromosome cells appear to be produced wholly, or almost wholly, 
by one of the two sexes; this is clearly female in certain cases, but we 
may find that these cells are male in others.^^ Without considering 
the question of whether these forms, when given off as Lamarckiana 
mutants are "half mutants" (de Vries), it is clear that a Lamarckiana 
offspring is produced by selfed 15-chromosome mutant derivatives of 
O. Lamarckiana when two gametes, each bearing Lamarckiana char- 
acters, and, possibly, the chromosomal combination peculiar to these 
gametes, unite and produce a seed capable of germinating. Bartlett 
('15a), after stating that certain mutants appear to produce two kinds 
of eggs, one carrying the characters of the mutant producing them and 
the other the characters of the parent species, while the pollen grains 
appear to be of one kind only and to carry the characters of the parent 
species, adds: "If so, Oe. lata might be supposed to originate by the 
union of a lata-egg (itself constituting the true mutation) with a 
Lamar ckiana-sperm.'' Accepting Bartlett's suggestion, it may be 
said of all 15-chromosome mutant derivatives of 0. Lamarckiana 
which, when selfed, produce two types of offspring, one duplicating 
the characters of the mutant parent and the other those of 0. Lamarcki- 
ana, that an offspring of the first type is obtained from these forms, 
selfed, when an 8-chromosome gamete bearing the characters of the 
mutant parent, and, possibly, the chromosomal combination peculiar 
to these gametes, unites with a 7-chromosome gamete bearing La- 
marckiana characters, and possibly, the chromosomal combination 
peculiar to Lamarckiana gametes, and produces a seed capable of ger- 
minating. If we consider this matter on a strictly chromosomal 
basis, we will concede, of course, that 9 + 6, or any other union which 
produces the same chromosomal combination as the ordinary 8+7, 
might result in an offspring which would duplicate the vegetative char- 
acters of the 15-chromosome parent. However, since 14-chromosome 
offspring of i^-chromosome plants and i^-chromosome offspring of 14- 
capable of functioning, are bearers of Lamarckiana characters. It is probable that 
7-chromosome Lamarckiana gametes (of one sex) are produced by 0. alhida, but ex- 
perimental evidence has not indicated the facts in the case. 
2^ Doubtless these assertions, and the conclusions regarding 0. lata under the 
heads of (a), (6) and (c) on page 87 would be equally applicable to many other 
15-chromosome mutant derivatives of 0. Lamarckiana, if the names of these mutants* 
in the latter case, were substituted for that of 0. lata. 
