io8 
ANNE M. LUTZ 
5365, all found in cultures of O. lata, selfed. In addition to the fore- 
going, type 2806, having many points in common with type 5509, 
also has 15 chromosomes. 
4. Of the above 12 types (11 of which were quite distinct) now 
known to have 15 chromosomes, only two are Za/a-like; namely, 
O. lata and 0. nanella lata. 
5. Certain somatic characters of many mutant offspring of 0. La- 
mar ckiana X 0. Lamarckiana and 0. Lamar ckiana, selfed, indicate 
that a very large percentage of the mutant offspring of 0. Lamarckiana 
have 15 chromosomes and that a larger number of 15- than of 14-chro- 
mosome mutant offspring are produced by this form. Not only does 
there appear to be a larger number of distinct types of 15- than of 14- 
chromosome mutants, but a higher percentage of 15- than of 14-chro- 
mosome individuals produced by 0, Lamarckiana. Only a small 
percentage of the former may be classed as lata-\\ke, or as semilata- 
like, forms. 
6. While /a/a-like forms are commonly characterized by 15 chro- 
mosomes, three distinct types have been found in Cold Spring Harbor 
cultures with 16 chromosomes. Two appeared in separate cultures of 
0. Lamarckiana X 0. Lamarckiana (1908 and 1910) and one among 
the offspring of 0. lata, selfed (1910). 
7. Owing to the fact that 15-chromosome forms are very often 
male-sterile, or produce but little pollen capable of functioning, their 
constancy has not been tested upon an extensive scale. 15-chromo- 
some mutants 0. lata, 0. semilata Gates, 0. lata ruhricalyx, 0. bipartita 
and 15 (?) -chromosome 0. elliptica, are known to be inconstant, while 
de Vries's researches indicate that 15-chromosome 0. alhida and 14- 
or 15-chromosome 0. ohlonga are constant. 
8. The evidence available at present indicates that most 14-chro- 
mosome forms are constant and most 15-chromosome forms incon- 
stant. Furthermore, the available evidence indicates that inconstancy 
is commonly associated with the 14 +-chromosome condition. It 
seems, however, that forms having twice 14 chromosomes are more 
likely to be constant in the same sense that de Vries's 0. gigas is 
constant, than those having more than 14, but fewer than 28, chromo- 
somes. 
9. While it is probable that we shall find that most forms having 
an odd number of chromosomes are inconstant, whether the number 
be 15 or 15 +, it does not follow that forms having an even number 
