ON THE QUICK GROWING WALNUT 
perimenters who have paid attention only to a few 
conspicuous characters that Mendelize, that all 
possible combinations of characters will occur 
among the second generation hybrids, provided 
only enough of these are produced. 
Possibly this statement is correct. But it is not 
susceptible of demonstration because it would not 
be feasible to produce enough individuals in a 
single generation to put it to the test. For the num- 
ber of possible combinations increases in geo- 
metrical ratio, as we have seen, with the increased 
number of characters under consideration. Anda 
really penetrating view of the situation reveals to 
us hereditary factors in the germ-plasm of each 
individual plant that would be numbered, could 
we isolate them, not merely by tens or scores; not 
merely by hundreds or thousands; but rather by 
hundreds of thousands or millions. 
Such a statement probably will not surprise any 
cne who has read the various preceding chapters 
in which we have viewed various aspects of her- 
edity. But to those experimenters who have been 
prone to think of “unit characters” as few in num- 
ber, such a statement will perhaps seem anoma- 
lous. Yet there can be no question that it is fully 
justified. 
In point of fact, what the present day student 
of heredity usually speaks of as a unit character 
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