Breeders generally prefer to fertilize hybrids with the
pollen of their parents. But this operation is to be considered as a new
cross, and consequently is wholly excluded from our present discussion.
Hence it follows that a clear insight into the heredity of hybrids may
be expected only from scientific experiments. Furthermore some of the
diversity observed as a result of ordinary crosses, may be due to the
instability of the parents themselves or at least of one of them, since
breeders ordinarily choose for their crosses some already very variable
strain. Combining such a strain with the desirable qualities of some
newly imported species, a new strain may [287] result, having the new
attribute in addition to all the variability of the old types. In
scientific experiments made for the purpose of investigating the general
laws of hybridity, such complex cases are therefore to be wholly
excluded. The hereditary purity of the parents must be considered as one
of the first conditions of success.
Moreover the progeny must be numerous, since neither constancy, nor the
exact proportions in the case of instability, can be determined with a
small lot of plants.
Finally, and in order to come to a definite choice of research material,
we should keep in mind that the chief object is to ascertain the
relation of the offspring to their parents.
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