784 ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
Fig. 4. 
from the base of the spur, up and down 
the branch and also, more slowly, around 
it. The inner parts of the bark and the 
cambium become affected and a typical 
canker of small size results. Very often 
girdling follows and the whole end of a 
branch may be killed by a canker at its 
base. Practically all of the dead shoots 
which so often appear in the top of a 
tree during the year, seem to be caused 
by cankers spreading out from spurs or 
buds that died in some previous season 
or at the beginning of the same season. 
Pseudomonas cerasus, Griffin, the Cause 
of Spur Blight 
In March, 1909, Mr. F. L. Griffin found 
bacteria associated with blight of cherry 
buds. Inoculations with cultures pro- 
duced the characteristic blight. Repeated 
tests were made during the next two sea- 
sons with buds from various districts, 
with the same results. Careful morpho- 
logical and physiological studies led him 
to believe that a new species had been 
discovered and he accordingly described 
it under the name Pseudomonas cerasus. 
This organism, then, seems to be the 
cause of one form of cherry gummosis. 
How much it has to do with other phases 
of the disease only further investigation 
can show.* 
Recent Experiments and Observations 
In February, 1912, the writer began 
his investigation of cherry gummosis and 
* See Science, N. S. 34, No. 879, p. 615, No- 
vember 3, 1911. 
Examples of Spur Blight Due to Bacteria. 
from the dead spurs. 
| Exp 
Drops and masses of gum ooze out 
since that time has confirmed many of 
Mr. Griffin’s previous. observations and 
conclusions. Furthermore, the repeated 
discovery of bacteria similar to Ps. cer- 
asus in the diseased areas on trunks, 
limbs or twigs, and the production of 
gumming by subsequent inoculation with 
these organisms, gives strong support to 
the idea that bacteria cause the character- 
istic injuries found on the bodies of trees 
affected with this disease. 
Summary of Experiments and 
Observations 
To sum up the result briefly: 1. The 
experiments of Mr. Griffin and the writer 
seem to indicate that a species of bac- 
terium (Ps. cerasus) is responsible for 
the blighting and gumming of buds and 
spurs on common varieties of the sweet 
cherry. 2. This bacterium is also able 
to induce gumming when _ inoculated 
into the body and branches of these vari- 
eties. 38. Bacteria similar to Ps. cerasus 
have been found during the spring in 
nearly all spreading cankers on _ the 
trunks and limbs as well as in diseased 
spurs, and these, by inoculation into 
healthy trees, are able to induce gum- 
ming. 4. From observations made through 
one season only, it appears that the dis- 
ease progresses rapidly in the spring and 
only slowly or not at all during the sum- 
mer and autumn. 5. It is impossible to 
state positively from our present knowl- 
edge that bacteria are responsible for all 
the more serious phases of the disease on 
