[31] [Mendel throughout speaks of his cross-bred Peas as “hybrids,” a
term which many restrict to the offspring of two distinct _species_.
He, as he explains, held this to be only a question of degree.]
Experiments which in previous years were made with ornamental plants
have already afforded evidence that the hybrids, as a rule, are not
exactly intermediate between the parental species. With some of the
more striking characters, those, for instance, which relate to the form
and size of the leaves, the pubescence of the several parts, &c., the
intermediate, indeed, was nearly always to be seen; in other cases,
however, one of the two parental characters was so preponderant that it
was difficult, or quite impossible, to detect the other in the hybrid.
This is precisely the case with the Pea hybrids. In the case of each
of the seven crosses the hybrid-character resembles[32] that of one of
the parental forms so closely that the other either escapes observation
completely or cannot be detected with certainty. This circumstance is
of great importance in the determination and classification of the
forms under which the offspring of the hybrids appear. Henceforth in
this paper those characters which are transmitted entire, or almost
unchanged in the hybridisation, and therefore in themselves constitute
the characters of the hybrid, are termed the _dominant_, and those
which become latent in the process _recessive_. The expression
“recessive” has been chosen because the characters thereby designated
withdraw or entirely disappear in the hybrids, but nevertheless
reappear unchanged in their progeny, as will be demonstrated later on.
[32] [Note that Mendel, with true penetration, avoids speaking of the
hybrid-character as “transmitted” by either parent, thus escaping the
error pervading modern views of heredity.]
It was furthermore shown by the whole of the experiments that it is
perfectly immaterial whether the dominant character belong to the
seed-bearer or to the pollen parent; the form of the hybrid remains
identical in both cases. This interesting fact was also emphasised by
Gärtner, with the remark that even the most practised expert is not in
a position to determine in a hybrid which of the two parental species
was the seed or the pollen plant[33].
[33] [Gärtner, p. 223.]
Of the differentiating characters which were used in the experiments
the following are dominant:
1. The round or roundish form of the seed with or without shallow
depressions.