414 BOTANICAL GAZETTE [MAY 
a consideration of the mutation of O. Lamarckiana gigas into its 
dwarf mutants (8). These spring from the self-fertilized strain of 
O. gigas in about 1-2 per cent of the offspring of every generation, 
and have done so since the very origin of the parent form. Arti- 
ficially crossed with their parent, they produce hybrids of high 
stature, which are not externally distinguishable from O. gigas 
itself, and which split, in the next generation, into three types, 
according to the formula of Mendel for the monohybrids. Assum- 
ing, as is now generally conceded, that mutations take place before 
fecundation, we can easily see that the gametes of O. gigas which 
mutated into manella must for some part be united in fecundation 
with normal sexual cells. Such combinations must produce half 
mutants, as I called them in my book Gruppenweise Artbildung,° or 
mutant hybrids, as they have since been called (8, p. 345), and 
these will split in the next generation into about one-fourth dwarts, 
one-fourth high and normal gigas, and one-half new mutant 
hybrids. The latter will continue to reproduce the splitting in the 
succeeding generations, and this may obviously be repeated during 
an unlimited number of successive years. 
If we now suppose that, by means of some contrivance, the 
dwarfs and the constant high specimens were yearly eliminated 
before flowering, we should have a race which would produce in 
every generation about one-fourth dwarfs. The phenomenon 
would then be an instance of mass mutation, and we may choose 
it as the prototype from which to explain our observations on 
O. grandiflora. From our point of view the splitting would be a 
repeated appearance of the dwarf mutants, due to the original 
mutation of one gamete. For this reason we shall call it a secondary 
mutation. 
Let us now consider the strain of O. grandiflora, found in 1912 
near Castleberry, Alabama, as such a mutant hybrid, originally 
produced by the mutation of a sexual cell into ochracea and its 
copulation with a normal gamete of the strain. Whether this 
initial mutation took place a few or many years before 1912 is of 
course without interest for this discussion. It may even be older 
6 The case is especially clear in the instance of O. Lamarckiana semigigas, where 
the half mutants with their 21 chromosomes are obviously the result of the copulation 
of normal gametes with others mutated into gigas. 
