4 
Bulletin 86. 
tation of a slime mould, one of the lower forms of fungi. He 
was able to produce galls at will on young seedlings by inoculat¬ 
ing them with bits of the galls, also by planting seedlings in 
sterile soil and then placing pieces of minced galls about their 
roots. Under certain conditions minute reproductive bodies are 
formed on the surface of the galls, which easily work their way 
through damp soil, or may be carried by irrigation water from 
tree to tree. Particles of the galls may also be carried by culti¬ 
vators and other tools, so that it is easy to conceive how the 
disease may spread from a single infected tree to all the trees in an 
orchard. 
Indications also point to the conclusion that the organism 
may remain alive for some time in decayed galls, or in galls on 
dead trees, or on diseased trees that have been removed from the 
orchard. 
It is difficult to estimate the amount of damage that crown 
gall is responsible for, as it is a disease that is commonly over¬ 
looked, and then it is usually several years after infection that the 
apparent vigor of the tree is affected. Reports from a number of 
the County Horticultural Inspectors, as well as personal observa¬ 
tions, show that crown gall is a common disease in Colorado. It 
is evident, also, from what has been said, that the effects of the 
disease will become more apparent as the orchards grow older. 
Prof. Tourney has the following to say about the amount of 
damage that can be attributed to the disease : 
The seriousness of crown gall in various and widely separated portions 
of the country, is certainly indicative of an enormous annual loss to the fruit 
industry. In estimating the amount of damage done by crown gall, considera¬ 
tion must be given to the fact that it usually occurs underground, and is rarely 
seen except when the trees are taken from the nursery, or when excavations are 
made at the crowns. The majority of diseased trees live on year after year, but 
make less growth and in all probability produce less and poorer fruit than 
healthy trees. It is not sufficient for a tree to simply live. It must grow and 
ruit abundantly to be profitable. The total annual loss from this disease in 
this country in all probability reaches the enormous sum of from $500,000 to 
$1,000,000, possibly much more. 
Crown gall is found on a variety of plants, including almond, 
apple, apricot, blackberry, cherry, chestnut, English walnut, 
grape, peach, pear, plum, poplar and raspberry. In the experi¬ 
ments above mentioned, it was found that the disease could be 
transferred readily from the almond to apricot and peach trees, 
thus indicating that the same organism is responsible for crown 
gall on these three hosts. Serious investigation of the galls on 
the other trees and plants have not yet been undertaken, but it is 
likely that the disease is of the same nature, if not induced by 
the same organism. It is to be hoped that this point may soon 
be established, as it is important to know, for instance, whether 
diseased raspberry and blackberry bushes, when planted in an 
orchard, may not be the means of infecting the trees, or, in the 
