m off sharply from the earlier hybridisers. He realised that their
failure to elucidate any general principle of heredity from the results of
cross fertilisation was due to their not having concentrated upon
particular characters or traced them carefully through a sequence of
generations. That source of failure he was careful to avoid, and throughout
his experiments he crossed plants presenting sharply contrasted characters,
and devoted his efforts to observing the behaviour of these characters in
successive generations. Thus in one series of experiments he concentrated
his attention on the transmission of the characters tallness and dwarfness,
neglecting in so far as these experiments were concerned any other
characters in which the parent plants might differ from one another. For
this purpose he chose two strains of peas, one of about 6 feet in height,
and another of about 1-1/2 feet. Previous testing had shown that each
strain bred true to its peculiar height. These two strains were
artificially crossed[1] with one another, and it was found to make no
difference which was used as the pollen parent and which was used as the
ovule parent. In either case the result was the same. The result of
crossing tall with dwarf was in every case nothing but talls, as tall or
even a little taller than the tall parent. For this reason Mendel termed
tallness the DOMINANT and {19} dwarfness the RECESSIVE character. The next
stage was to collect and sow the seeds of these tall hybrids. Such seeds in
the following year gave rise to a mixed generation consisting of talls and
dwarfs _but no intermediates_. By raising a considerable number of such
plants Mendel was able to establish the fact that the number of talls which
occurred in this generation was almost exactly three times as great as the
number of the dwarfs. As in the previous year, seed were carefully
collected from this, the second hybrid generation, and in every case _the
seeds from each individual plant were harvested separately and separately
sown in the following year_. By this respect for the individuality of the
different plants, however closely they resembled one another, Mendel found
the clue that had eluded the efforts of all his predecessors. The seeds
collected from the dwarf recessives bred true, giving nothing but dwarfs.
And this was true for every dwarf tested. But with the talls it was quite
otherwise. Although indistinguishable in appearance, some of them bred
true