MUTATIONS 285 
less characters have been discovered that appear to be inherited according 
to simple Mendelian rules. We conclude, therefore, that some of the 
lamarckiana derivatives are the result of factor mutations. 
The cytological studies on GEnothera have yielded important infor- 
mation concerning the chromosome numbers of various species and “ mu- 
tants.” With reference to @. lamarckiana and its derivatives especially 
the chromosome counts of Miss Lutz, Gates, Davis and others are of 
great interest. Lamarckiana has 14 chromosomes as have also most, of 
the “mutants” which have been derived from it, but the sexually 
deficient and inconstant form, lata (see Fig. 116) has been found always 
to have 15 chromosomes. Furthermore, actual cases of a distribution 
of 6 + 8 chromosomes in the heterotypic division of pollen mother cells 
have been observed in lamarckiana and rubrinervis. It is safe to assume, 
therefore, that lata-like ‘mutants’ result from the union of a gamete 
containing 8 chromosomes and one containing the normal number, 7. 
There is also good evidence that Gf. gigas is the result of tetraploidy. 
Several different plants of this type have been found to contain 28 chromo- 
somes or thereabouts. However, there is a giant race of the Chinese 
primrose which has only 24 chromosomes, the number typical of the 
species, while another has 48 chromosomes. It seems then that gigan- 
tism is associated with tetraploidy but that it is not necessarily caused 
by an aberration in chromosome number. Thus we find that at least 
one, and perhaps another of the original lamarckiana derivatives are 
due to chromosome aberrations during meiosis. 
Of the nine original mutants we have now definitely classified two— 
brevistylis as a factor mutation and lata, the result of a departure from 
normal chromosome number, and we have found that a third, gigas, 
exhibits an extreme chromosome aberration. What about the remain- 
ing six—levifolia, albida, oblonga, rubrinervis, nanella and scintillans? 
There is no evidence of a simple factorial relation between them and the 
parent species. One-‘of them, sczntillans, must remain in the doubtful 
class until its chromosome numbers have been determined, but the 
inconstancy of this form suggests that it should be classed with lata 
and gigas under chromosome aberrations. The remaining five, levifolza, 
rubrinervis, nanella, oblonga and albida, are known to have 14 chromo- 
somes. Based on the evidence set forth in Chapter XII, it seems to 
us that one and only one category is open to these five forms and that 
probably albida, oblonga and most of the new forms that have appeared 
not only in cultures of lamarckiana and its derivatives but also in other 
species of Ginothera, are the result of chance recombinations of factors 
due to a condition of substrate hybridity. This expression, as has already 
been explained, is meant to imply that “mutating” species such as Z. 
lamarckiana are merely species hybrids which happen to result from 
combinations of different reaction systems such that the majority of 
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