each character, and if
the constitution of the original parents be known, the nature of the F_2
generation, _i.e._ the number of possible forms and the proportions in
which they occur, can be readily calculated. Moreover, as Mendel showed, we
can calculate also the chances of any given form breeding true. To this
point, however, we shall return later.

Of Mendel's experiments with beans it is sufficient to say here that they
corroborated his more ample work with peas. He 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 Naegeli the botanist. To the
breeding and crossing of bees he also devoted much {27} time and attention,
but unhappily the record of these experiments appears to have been lost.
The only other published work that we possess dealing with heredity is a
brief paper on some crossing experiments with the hawkweeds (_Hieracium_),
a genus that he chose for working with because of the enormous number of
forms under which it naturally exists. By crossing together the more
distinct varieties, he evidently hoped to produce some of these numerous
wild forms, and so throw light upon their origin and nature. In this hope
he was disappointed. Owing in part to the great technical difficulties
attending the cross fertilisation of these flowers he succeeded in
obtaining very few hybrids. Moreover, the behaviour of those which he did
obtain was quite contrary to what he had found in the peas. Instead of
giving a variety of forms in the F_2 generation, they bred true and
continued to do so as long as they were kept under observation. More recent
research has shown that this is due to a peculiar form of parthenogenesis
(cf. p. 135), and not to any failure of the characters to separate clearly
from one another in the gametes. Mendel, however, could not have known of
this, and his inability to discover in _Hieracium_ any indication of the
rule which he had found to hold good for both peas and beans must have been
a source of considerable disappointment. Whether for this reason, or owing
to the utter neglect of his work by the scientific world, Mendel gave up
his experimental {28} researches during the latter part of his life. His
closing years were shadowed with ill-health and embittered by a controversy
with the Government on a question of the rights of his monastery. He died
of Bright's disease in 1884.

_Note._--Shortly after the di