graves: breeding trees for disease resistance 
99 
of its progeny have been tested. This particular cion was No. 24 in 
their series of elms. It has now been named Elm Christine Buisman. 
If they have succeeded in getting any other resistant elms of the Euro¬ 
pean type, I am not aware of it. As far as I know they have not under¬ 
taken any crossing of species of elms. Nothing in the literature that 
they have published would indicate it and I cannot remember seeing 
anything when I was in the Netherlands that would lead me to believe 
that they had.” 
I quote also from an article by Dr. Beattie in American Forests for 
April, 1937, p. 160, which gives some additional facts. 
“Dutch investigators are making an energetic and thorough search 
for resistant individuals of European species and for resistant elm 
species from other parts of the world which have characteristics that 
will make them useful as substitutes. 
A splendid collection of species, varieties and strains of elms has been 
assembled by the Willie Commelin Scholten Laboratory and the Park 
System of The Hague. These are propagated and grown in plantations 
in four different localities and are being systematically inoculated in 
large numbers with the elm disease fungus. Among European elms, the 
best results have been obtained with a strain of Ulmus campestris 
produced by vegetative propagation from a tree which came originally 
from Madrid, Spain. Among introduced species, the greatest resistance 
is found in the Siberian elm, Ulmus pumila, as it was in American inves¬ 
tigations. With these resistant trees and others later developed, the 
Dutch hope to replace their native elms. 
Unfortunately for the United States, the Dutch found that the various 
American species of elms are all susceptible to the disease and that the 
treasured American elm, Ulmus americana , with its unique vase form, is 
perhaps the most susceptible of them all. This is also confirmed by our 
work in America. However, it is possible that with the huge population 
of American elms in the United States, resistant individuals may be 
found.” 
It should be possible to cross pollinate these elm species and the sooner 
we start the work the better. A disease-resistant species like Ulmus 
pumila , the Siberian elm, should be crossed with the American elm. 
The object in view should be, in my opinion, to produce an elm of large 
size and beautiful vase-like outline, like our cherished American species, 
and at the same time resistant to the Dutch elm disease. 
