We here see
that the mere act of crossing two distinct plants does not by itself
benefit the offspring. This case is almost the converse of that in the
last paragraph, on which the offspring profited so greatly by a cross
with a fresh stock. A similar trial was made with the descendants of
Hero in the following generation, and with the same result. But the
trial cannot be fully trusted, owing to the extremely unhealthy
condition of the plants. Subject to this same serious cause of doubt,
even a cross with a fresh stock did not benefit the great-grandchildren
of Hero; and if this were really the case, it is the greatest anomaly
observed by me in all my experiments.
2. Mimulus luteus.
During the three first generations the intercrossed plants taken
together exceeded in height the self-fertilised taken together, in the
ratio of 100 to 65, and in fertility in a still higher degree. In the
fourth generation a new variety, which grew taller and had whiter and
larger flowers than the old varieties, began to prevail, especially
amongst the self-fertilised plants. This variety transmitted its
characters with remarkable fidelity, so that all the plants in the later
self-fertilised generations belonged to it. These consequently exceeded
the intercrossed plants considerably in height. Thus in the seventh
generation the intercrossed plants were to the self-fertilised in height
as 100 to 137.
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