FIFTEEN- AND SIXTEEN-CHROMOSOME OENOTHERA MUTANTS 97 
during reduction in 15-chromosome forms may result in the production 
of a greater number of 7- than of 8-chromosome female gametes and 
may partially account for the greater number of 14- than of 15- 
chromosome forms among the offspring of these plants selfed, and 
among those of 15-chromosome plants pollinated by 14-. 
Gates i'ogb) found all of the 21 chromosomes of the triploid forms 
which he studied were distributed to the two poles of the heterotypic 
spindle in groups of 10 and 11, ordinarily, and 9 and 12, occasionally, 
No evidences of degeneration were recorded. Geerts (' 1 1 ) , on the other 
hand, found that only 14 of the 21 chromosomes of the triploid 
hybrids which he examined were regularly distributed in groups of 
7 each, the remaining 7 fragmenting and degenerating. The observa- 
tions of these two workers being so unlike, the following statement was 
made by Lutz ('12, pp. 404-405): "The evidence does not indicate 
that we shall find one type of reduction exclusively in 21 -chromosome 
mutant A, for example, and another in a sister mutant B. It is 
possible . . . that the type of reduction present in the male and 
female germ cells of a flower depends upon its position on the plant. 
. . . For instance, the reduction division in both the male and female 
germ cells of the first flowers of a triploid plant might be represented' 
by the Gates type almost exclusively, while that of the late flowers on 
the same branch (or stem) might exhibit chiefly the Geerts type of 
reduction, or vice versa. Perhaps also, the first flowers of a weak 
lateral or sub-lateral branch may differ from the first flowers of the 
stem or a strong basal branch." An interview with Dr. Geerts later 
revealed the fact that his fixations had been prepared in September and 
October and that they had been taken from seed-plants, therefore 
from individuals which had produced their first flowers much earlier 
in the season; hence it was stated (p. 405) that "This indicates that 
Geerts's type of reduction appears in the later flowers, and Gates's 
probably in the earlier ones." Gates ('15a, p. 188) has since supported 
this assumption by the statement that the material from which his 
studies were made had been collected at the height of the flowering 
season. 
Gates and Miss Thomas ('14) have shown that one of the extra 
chromosomes of 0. lata and various lata-Vike forms sometimes degener- 
forms, that 8-chromosome male gametes are not produced by the latter. Perhaps 
all of the 8-chromosome pollen grains of 0. lata ruhricalyx and certain other 15-chro- 
mosome forms, whether seemingly good or not, are incapable of functioning. 
