In the second generation after the isolation of stray tricotylous
seedlings the average condition of the race is usually reached, but only
by some of the strongest individuals, and if we continue the race,
sowing or planting only from their offspring, the next generation will
show the ordinary type of variability, going upwards in some and
downwards in other instances. With the _Phacelia_ and the mercury and
some others I had the good luck in this one generation to reach as high
as nearly 90% of tricotylous seedlings, a figure indicating that the
normal dicotylous type had already become rare in the race. In other
cases 80% or nearly 80% was easily attained. Any further divergence from
the average would have required very much larger sowings, the effect of
selection between a limited number of parents being only to retain the
high degree once [423] reached; so for instance with the mercury, I had
three succeeding generations of selection after reaching the average of
55%, but their extremes gave no increasing advance, remaining at 86, 92
and 91%.
If we compare these results with the effects of selection in twisted and
fasciated races, we observe a marked contrast. Here they reached their
height at 30-40%, and no number of generations had the power of making
any further improvement.
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