The herald., 1893-06-01

thin-walled cells, with now and then the
distorted and ratrered elements of the
tibro-vascular buhdles.
young gall of this kind contains
very much water, and on driving, be-
comes epongelike in appearance, and is
very light and quite hard. Older knots
are similar, but harder, and dry into
harder and frmer masses, which do not
shrink or become spongelike. In size
the crown gall varies greatly. being
often as large ss ones fist and some-
times much larger, especially in the
apricot.
There ere several theories as to the
cause OF the crown gall, but none of them
are without very serious objections. One
idea is that these gals are the result of
wounds made in cultivation, and think
it has been proven that at least in few
cases the gals have followed such
wounds. In attempting to heal q wound,
as ID we'll known, the plant will often
produce at that point slight swelling.
and it is argued that at the crown the
conditions ere such that large swelling
Will result. There sre, however, a num-
Der of fatal objections to this hypothe-
sis. Neither is the crown gall the uni
form result of q wound, nor ia wound,
at least one made by human agency.
necessary to produce a gall, though it
would be bold to assert that there had
never been wound of any kind at the
point where the gall ia produced. The
most fatal objection to this hypothesis
is the fact that the appearance, the
manner OF growth and all the phenom-
ena connected with the crown gall are
SO different from those OF healing
wonnd that there seems scarcely any
reason to connect the two.
Another theory is that they are due to
peculiar conditions of the weather, such
as trosts, excessive rains and such things
at critical time in the spring, causing
an abnormal stagnation or an excessive
How OF sap, and the gall is the re-
suit. These suppositions are scarcely
reconcilable with the facts of plant
physiology, and it has never been OBJ
served that these gals are produced in
particular abundance Immediately fol-
lowing any peculiar spring condition.
Indeed, the idea seems to arise from the
general tendency to ascribe every abb
normal condition of plant to the
weather.
A third theory is that they are due to
some of the fungi related perhaps to that
which produces the true black knot.
The only objection to this theory is that
no such fungus has ever been observed
about the knots, atleast not in the living
knotH, and 1t may be that more CAREFUL
study than has yet been made will show
that such fungus does occur.
Finally, as has become quite the
fashion of late years, the bacteria have
been charged with the injury. myself
have succeeded in getting pure cultures
OF miorococcug from the inside of some
of the knots, after taking all the usual
precautions to prevent accidental con-
tamination. do not succeed, however,
with all knots OF this kind. and not hav-
ing further evidence, such ss, for
instance, the communication OF the dis
ease to healthy plants, we are not in a
position to say that we have found the
cause.
The presence of gall at the crown of
o plant seems to effect an obstruction to
the flow OF the ssp, and in this way a
tree or vine becomes weakened and
finally dies. The gall generally attacks
small plants, but not always, and il
often takes a number of years before the
plant is killed.
Being not quite sure OF the cause, it
ie, however, believed that the following
trestment is the safest procedure: First,
in the orchard the knots should be
carefully removed and burned az soon
as found, and an antiHeptic application
made to the tree where the knot has
been removed. We would recommend
Bordeaux mixture for this purpose.
Trees 60 treated should be examined
from time to time for at least year,
and should the knot reeppear, it would
be best to remove and destroy the whole
tree. When tree ie removed it would
be well to delay resetting for a year or
two, or to reset with tree of an unsus-
ceptible kind.
Second, when setting an orchard, re-
ject all stock affected by the knot.
would prefer to have stock from nurs-
cry known to be entirely free from it,
Third, in the nursery thegreatest care
should be taken to destroy by burning
everything showing any evidence of the
disease. Fields in which these gals
have appeared should be devoted to
some other crop for number of years.
Among those present were: O. L.
Hanson, OF the Chino Valley nursery;
John Burr, OF San Fernando; O. B.
Hewitt, Pasadena; J. Muir, Covina; W.
E. Collins, Ontario; John Scott. of
Duarte; 0. B. Richards, Moreno; Jud-
son Williams, Fallbrook Abbot Kinney,
Lamsnda; B. j. Perry, Santa Ana;
Hiram Hamilton, Orange; H. B. Mus
con, San Bernardino r. B. Kirchhoffer,
Ontario and many others.