of species
when
crossed
and of
their
hybrid
offspring.
It is
impossible
to study
the
several
memoirs
and works
of those
two
consci-
entious
and
admirable
observers,
K¨olreuter
and
Gartner,
who almost
devoted
their
lives to
this
subject,
without
being
deeply
impressed
with the
high gen-
erality of
some
degree of
sterility.
K¨olreuter
makes the
rule
universal;
but then
he cuts
the knot,
for in ten
cases in
which he
