The first is the size of the cultures required for the
resulting amelioration. In other words, would it have been possible to
attain an average of 20 rows in a single experiment? This is a matter of
calculation, and the calculation must be based upon the experience
related above, that the progression in the case of maize is equal to
two-fifths of the parental deviation. A cob with 20 rows means a
deviation of 7 from the average of 13, the incipient value of my race.
To reach such an average at once, an ear would be required with 7 x 5/2
= 17-1/2 rows above the average, or an ear with 30-32 rows. These never
occur, but the rule given in a previous lecture gives a method of
calculating the probability of their occurrence, or in other words, the
number of ears required to give a chance of finding such an ear. It
would take too long to give this calculation here, but I find that
approximately 12,000 ears would be required to give one with 28 rows,
which was the highest number attained in [784] my experiment, while
100,000 ears would afford a chance of one with 32 rows*. Had I been able
to secure and inspect this number of ears, perhaps I would have needed
only a year to get an average of 20 rows. This however, not being the
case, I have worked for seven years, but on the other hand have
cultivated all in all only about one thousand individuals for the entire
experiment.
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