and examining the wood, there was no evidence of
curly grain detectable either by casual personal observation or from
samples sent to the Forest Products Laboratory at Madison, Wisconsin.
This, of course, was a disappointment because J. F. Wilkinson had shown
samples of walnut grown from scions of the Lamb Walnut obtained from the
late W. B. Bixby which showed evidence of curly grain. A photograph of
the wood secured from Mr. Wilkinson is shown in figure 1. Wood samples
from a tree growing at Beltsville, Maryland, which was also secured from
Mr. Bixby by C. A. Reed, does not show evidence of curly grain.

The simplest explanation of the failure of the tree in Ithaca to show
curly grain would be that somehow the tree was not properly labelled or
that scions were mixed in propagation and that the trunk was not derived
from the original Lamb Curly Walnut. However, the fact that only a few
trees were concerned makes it improbable that trees were mislabelled in
the Ithaca planting and there is no good reason to believe that the tree
planted at Beltsville was not authentic.

[Illustration: Fig. 1. Radial face of wood of grafted Lamb black walnut
grown by J. F. Wilkinson. Wavy or curly grain is apparent on right side
which is the outer part of the log (about natural size).]

Another possibility is that the original Lamb Walnut was a chimera. Such
a tree would have mixed tissues in its growing points, some having the
curly grain character and others not. In such a tree some scions would
produce curliness and others straight grain. It may be that these were
mixed in the original collection.

A third possibility is that curliness is produced by the interaction of
several factors, one a tendency to curliness inherent in the Lamb tree
and the others environmental such as growth rate, nutrient supply, the
nature of the soil or other such conditions.

Theoretically curly grain in walnut or any other tree is related to the
nature of the growth of the cambium layer. In normal growth the cells of
this layer are much elongated as seen in tangential section and are
relatively straight. The nature of these cambium cells is shown in
figure 2.

[Illustration: Fig. 2. The cambium of a straight-grained black walnut
tree as seen in tangential section. The nature and regularity of these
cells determines the nature and regularity of the cells of adjacent wood
and bark (x 150).]

It is well known from studies of cambial growth that irregul