OENOTHERA MUTANTS WITH DIMINUTIVE CHROMOSOMES 519 
Should a fragment of the 8th chromosome chance to persist, a 7+^- 
pollen grain might be formed.^ 
Thus far, no 14+^-chromosome offspring of 0. Lamarckiana has 
been reported; hence it is probable that the small chromosome of the 
three 14+^-chromosome mutants was derived from the lata mother 
in each case. Whatever its origin, as a somatic body, it is capable of 
dividing longitudinally and of performing other normal activities of 
ordinary chromosomes during cell division. 
4. Fate of the Small Chromosome in Succeeding Generations 
During the years in which this work was conducted at the Station 
for Experimental Evolution, Dr. G. H. Shull kindly gave me the 
privilege of studying all forms of interest which appeared in his cultures 
of Oenothera, and it was among his lata X Lamarckiana hybrids that 
No. 3878 appeared in 1908. With perseverance I succeeded in ob- 
taining a few seeds from this plant, selfed, and the offspring were 
grown by Dr. Shull in 1909. However, since the somatic chromosome 
number of the parent was not determined until late autumn of that 
year, the importance of determining the chromosome numbers of the 
offspring was not appreciated until the season had passed, conse- 
quently no fixations were prepared and no records of the vegetative 
characters of these plants are in my possession. The fate of the small 
chromosome is, therefore, unknown. 
Did a portion or all of the offspring of No. 3878, selfed, have 14+^- 
chromosomes? Since Geerts found that 7 whole (male and female) 
chromosomes of 21 -chromosome forms may be eliminated and Gates 
and Miss Thomas have shown that i or more of the ordinary (male) 
chromosomes of 15-chromosome forms may fragment and degenerate, 
it is probable that the small chromosome of 14+^-chromosome forms 
is eliminated in a similar manner, in many cases, at least. If a 
portion of the male and female gametes had 7+^-chromosomes and the 
remainder 7, then it is possible that 14-, 14+^- and i4+2_chromosome 
forms were produced.^ We know that 14-, 15- and i6-chromosome 
^ Likewise, it is possible that 7+i-chromosome female gametes are occasionally 
produced in this manner by 14-chromosome forms. All facts considered, it is more 
probable that 7+^-chromosome female gametes, capable of functioning, than that 
7+i-chromosome male gametes, capable of functioning, are produced by 0. Lam- 
arckiana and other 14- or 15-chromosome forms. 
* If 7+^-chromosome gametes are produced by 14+^-chromosome forms, it is 
probable that they are unisexual. 
