458 
and many other cultivated and wild 
plants, herbaceous as well as woody. It 
is very common on members of the rose 
family (Rosaceae) to which all of our 
ordinary tree fruits and many of our 
small fruits belong. Besides the plants 
above mentioned, it is reported as at- 
tacking the grape, walnut, chestnut, pop- 
lar, willow and alder. In the North- 
west it is known on practically all of 
our tree fruits, is found on blackberries, 
raspberries, loganberries and grapes, and 
also on the hop. The usual effect upon 
these different hosts is the production 
of tumors or galls, which are in general 
k  Bew. Bag. Ste 
Fig. 1. A, Crown Gall on the Canes of Grape. 
B, Crown Galls on the Peach Root of a 
Prune Tree. C, Crown Gall on a Loganberry 
Root. 
somewhat similar in form and appear- 
ance. The galls, as a rule, have an an- 
nual development, that is, they begin to 
form in the spring as the tree starts 
active growth and cease development in 
the fall. At first they are small, nearly 
spherical masses of more or less suc- 
culent tissue, whitish or translucent in 
appearance but rapidly becoming darker 
and uneven, till at maturity they are 
dark brown and warted. When occur- 
ring on small roots they may be only 
about one-quarter inch in diameter, while 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
on nursery stock, raspberries, etc., they 
may be about the size of a walnut. On 
large trees in the orchard they may 
reach a much greater diameter. The 
galls usually occur at the base of the 
trunk or on the roots, though in some 
plants they are found on the stems or 
branches above ground. The most com- 
mon point of attack, however is just 
beneath the ground at the crown of the 
plant. A peculiar form of the disease 
known as hairy root occurs commonly 
on the apple. 
The effects of an attack of this dis- 
ease are much more serious on certain 
kinds of plants than upon others and 
even among individuals of the same kind 
there are wide variations in the result- 
ing amount of damage. In some cases 
trees may be affected without giving any 
signs of harmful effect upon growth or 
production of fruit. In other cases, trees 
or smaller plants are often stunted and 
unprofitable and not infrequently die as 
a result of the presence of the galls. 
There are also many well-authenticated 
instances where trees known to be bad- 
ly affected with crown gall have exper- 
ienced apparently complete’ recovery. 
Furthermore, some of the serious ill ef- 
fects attributed to this disease must of- 
ten, on careful investigation, be charged 
to other troubles which have had entrance 
through the unprotected or decayed gall. 
The fire blight bacteria, mushroom root 
rot, wound parasites and heart rot fungi 
of various sorts as well as certain insects 
have easy access to a tree through galls 
where a healthy bark would have pre- 
vented any attack, and in most cases 
these secondary intruders are liable to 
have more serious consequences for the 
tree than the mere presence of the gall. 
It is supposed also that the disease may . 
appear in severe or in light form, depend- 
ing upon the virulence of the strain of 
organism producing the infection. 
The detrimental effect of the crown gall 
itself may arise in several ways. The. 
tumors rob the plant of some nutriment. 
Excessive evaporation of moisture may 
occur from the unprotected gall surfaces, 
especially where aerial galls are abund- 
