As I used pollen of unequal maturity for crossing and
self-fertilising the parent-plants, it is possible that the great
difference in the growth of their offspring may have been due to this
cause. In the next generation this source of error was avoided, and many
more plants were raised, and now the average height of the twenty-three
crossed plants was to that of the twenty-three self-fertilised plants as
100 to 91. We can therefore hardly doubt that a cross is beneficial to
this species.
3. Petunia violacea (third generation).
Eight crossed plants were to eight self-fertilised of the third
generation in average height as 100 to 131; and at an early age the
crossed were inferior even in a still higher degree. But it is a
remarkable fact that in one pot in which plants of both lots grew
extremely crowded, the crossed were thrice as tall as the
self-fertilised. As in the two preceding and two succeeding generations,
as well as with plants raised by a crossed with a fresh stock, the
crossed greatly exceeded the self-fertilised in height, weight, and
fertility (when these two latter points were attended to), the present
case must be looked at as an anomaly not affecting the general rule. The
most probable explanation is that the seeds from which the crossed
plants of the third generation were raised were not well ripened; for I
have observed an analogous case with Iberis.
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