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CARL D. LA RUE AND H. H. BARTLETT 
but has brought it about that the different lines composing the cultures 
have not all been carried the same number of generations since the 
foundation of the pedigree in 1910. The oldest lines have now been 
carried through six generations by self-pollination. 
At the close of the season of 1914 the cultures of Oe. Reynoldsii had 
been maintained for four generations, and the pedigree, as summarized 
in the former paper, ^ showed clearly that the individuals of f. typica, 
externally alike, were of two kinds, giving rise, respectively, to uniform 
and polymorphic progenies It had been shown, also, that both kinds 
of f. typica occurred in polymorphic progenies. One point, however, 
was still obscure. The original mass-mutant individual of f. typica 
had been the only plant of its generation self-pollinated for continuing 
the line, and it was therefore uncertain whether the sister plants of 
the same culture would have resembled it in giving rise to polymorphic 
progenies or would have given uniform progenies. In other words, 
was the original mass-mutant individual of f . typica itself of the nature 
of a rare physiological mutation? In order to answer this question it 
was necessary to go back to old seeds and retrace two generations. 
This has been done, with the result that two sister plants of the original 
mass-mutant individual have given two generations of uniform progeny. 
(It should be noted that here, as well as in the explanation of the 
pedigree, Figure i, a progeny is for convenience termed uniform, as 
opposed to polymorphic, even if it contains a few mutations, provided 
the mutability was unaccompanied by unusual seed sterility. The 
sporadic mutations that have appeared in so-called uniform progenies 
have in no case been those characteristic of mass mutability. No 
confusion can possibly arise from this terminology for the reason that 
Table I gives a detailed analysis of every culture concerned in the 
experiments.) It is therefore possible to conclude that mutating and 
non-mutating individuals of f. typica may occur together in either 
uniform or polymorphic progenies. In the former case the mutating 
individual must itself be regarded as a physiological mutation, or 
perhaps even as a premutation in the sense of De Vries.^ 
Premutation, according to De Vries, is the process of preparation 
for mutation. In forms showing ordinary mutability the various 
mutational types occur in every sufficiently large progeny in every 
generation, and the process of premutation must therefore be assumed 
to have taken place far back, and to have brought about a hereditary 
^ De Vries, Gruppenweise Artbildung, pp. 9 and 10, 335, 346. 
