MUTATION IN MATTHIOLA ANNUA, A MENDELIZING SPECIES 383 
tinct from those shiftings which produce ordinary MendeHan phe- 
nomena. Whether past hybridization has made these mutative 
changes possible, is an open question; we know that new types may be 
formed by hybridization, but the known methods of such type-for- 
mation seem to be out of the question here. 
Finally, it should be noted that in most of these cases the mutative 
change has far-reaching effects, modifying various characteristics of 
the plant. Notwithstanding this fact, the factor for the new type is 
regularly inherited as a unit, and sometimes shows linkage with another 
factor-pair, so we may suppose that the essential change is limited, 
in some cases at least, to a portion of one chromosome. 
University of California, 
Citrus Experiment Station, Riverside 
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