o variety which I had
grafted on butternut roots. The tree had been bearing for three or four
years but this was the first year the nuts had matured. During their
bearing period, these black walnuts had gradually changed in appearance,
becoming elongated and very deeply and sharply corrugated like
butternuts although they still retained the black walnut flavor. Because
of this mixture of characteristics, the government experts had great
difficulty in identifying the variety, although the Ohio was well known
to them.

Another variety of black walnut, the Thomas, I have also known to be
influenced by the butternut stock on which it was grafted, when in 1938,
one of my trees bore black walnuts whose meat had lost its
characteristic flavor and assumed that of the butternut.

[Illustration: _A--Genuine original Ohio Black Walnut from parent tree_

_B--Nut produced by grafting Ohio on Butternut_]

I also liked to pick hazelnuts when I was a boy. These are probably the
least interesting among the wild nuts since they are usually small and
hard to crack. There is much variation in wild hazels, however, and many
people may recall them as being reasonably large. One of the two species
abundant in Minnesota, _Corylus cornuta_ or Beak hazel, has fine,
needle-like hairs on its husk which are sure to stick into one's fingers
disagreeably. When the husk is removed, _Corylus cornuta_ resembles a
small acorn. It does not produce in southern Minnesota and central
Wisconsin as well as the common hazel, _Corylus Americana_, does, nor is
its flavor as pleasing to most people. It is lighter in color than the
common hazel and has a thinner shell. Of course, some hazels are
intermediate or natural hybrids between these two species, and if the
nuts of such hybrids are planted, they generally revert to one of the
parents when mature enough to bear. This natural hybridization occurs
among all plants, between those of the same species, the same genera or
the same family. It is very rare between plants of different families.
The process is a very important one in horticulture and I shall explain
some of the crosses which are well-known later in this book.

Chapter 2

FIRST ATTEMPTS

When I was about fifteen years old, my family moved to St. Paul,
Minnesota, where my home now is and where my experimental work with nuts
was begun. St. Paul is in the 45th north parallel, but although it is
farther north, it is as favorable for the grow