FOUNDERS OF PLANT BREEDING 
307 
failure he was careful to avoid and throughout his experiments 
he crossed plants presenting sharply contrasted characters, and 
devoted his efforts to observing the behavior 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 about six feet in height, and another of about 
one and one-half feet. Previous testing had shown that each strain 
bred true to its peculiar height. These two strains were artificially 
crossed 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 tails, as 
tall as or even a little taller than the tall parent. For this reason 
Mendel termed tallness the dominant and 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 tails and dwarfs but no inter- 
mediates. By raising a considerable number of each plant, Men- 
del was able to establish the fact that the number of tails which 
occurred in this generation was almost exactly three times as 
great as the number of dwarfs. As in the previous year, seeds 
were carefully collected from this, the second hybrid . generation, 
and in every case the seeds from each individual plant were har- 
vested 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 recessive bred true, giving nothing but dwarfs. 
And this was true for every dwarf tested. But with the tails it 
was quite otherwise. Although indistinguishable in appearance, 
some of them bred true, while others behaved like the original 
tall hybrids, giving a generation consisting of tails and dwarfs in 
the proportion of three of the former to one of the latter. 
Mendel is also known to have made experiments with many 
other plants, and a few* of his results are incidentally given in 
his series of letters to Nageli the botanist. The only other pub- 
lished work that we possess dealing with heredity is a brief paper 
on some crossing experiments with the hawkweeds (Hieracium ) , 
