134 
THE NATIONAL NURSERYMAN 
twelve per cent. This is as far as the investigations of the 
subject had gone up to the appearance of Dr. Hedgcock’s 
bulletin. 
PATHOLOGY OF KNOTS AND TUBERCLES 
The present bulletin recites the pathological history of 
knots and tubercles on the roots and stems of trees in 
Europe and this country, and arrives at the conclusion that 
all these knotty growths are the result of bacteria. The 
discovery of the bacteria was brought about by the examina¬ 
tion of marguerites or Paris daisy plants affected with gall¬ 
like growths on various parts of the stems and leaves. 
Galls on this type of plant is a far cry from galls on the roots 
of apple trees, but the investigators proved conclusively 
that the bacterium found in these galls was readily com¬ 
municable to other daisy plants, and, still'more surprising^ 
to a great variety of plants in nowise related. Beginning 
with inoculations on the same type. Dr. Smith tested salsify, 
potato, tobacco, oleander, olive, various vegetables, grapes, 
peaches, almond, raspberry, blackberry, chestnut, walnut, 
and many others. The results of these inoculations were 
not absolutely uniform. In most cases the characteristic 
reaction occurred, that is to say, the galls or knots developed 
but in some cases no growth occurred. Conversely, inocula¬ 
tions from the peach gall were made on the daisy and the 
knots were thus produced. It appeared easier to inoculate 
peach from peach galls than to inoculate more distantly 
related plants. Apples were infected with the knot from 
peach galls in several cases, as were also red raspberry, 
black raspberry, rose, magnolia, and red oak. The bulletin 
gives in detail the actual results covering this work, which 
has been going on since November, 1904. 
SYNOPSIS OF CONCLUSIONS RESPECTING CROWN-GALL 
“Crown-gall is a disease common in nurseries on the roots 
and shoots of various plants, and likely to continue on the 
plants when they are removed to orchards, vineyards, 
gardens, and hot-houses. It also occurs on various field 
crops. This name is used for the disease whatever the 
situation of the galls on the plant. 
The first successful isolations and infections were 
obtained in igo6, and the biology of the bacterial organism 
derived from the daisy has been determined more carefully 
than that from galls on other hosts. 
Hundreds of pure-culture inoculations on daisy have 
removed the subject from the domain of speculation and 
shown that the galls on Paris daisy are due to a white 
schizomycete named Bacterium tumefaciens (April, 1907). 
This organism is a short rod multiplying by fission and 
motile by means of polar flagella. It can be grown in many 
sorts of culture media, but does not live very long upon agar. 
It forms small, round, white colonies in agar or gelatin 
poured plates. Under unfavorable conditions of growth it 
readily develops involution forms. 
This schizomycete differs from many bacterial organisms 
in not producing open cavities in the plant. It appears to 
occupy the living cells in small quantities, causing rapid 
proliferation. 
It produces galls most readily in soft, .rapidly growing 
tissues. Ordinarily, resting tissues can not be made to pro¬ 
duce galls. Turnips seem to be an exception. 
Cross-inoculation to plants of other families have shown 
the daisy organism to be capable of inducing tumors on 
many species in widely separate parts of the natural system 
(Compositag to Salicaceae), these galls varying somewhat in 
appearance. 
Some species of plants were not infected (onion, fig, 
olive), and possibly are not infectable, but further experi¬ 
ments should be made. 
For purposes of comparison natural galls have also been 
studied on the following plants: Peach, apple, rose, quince, 
honeysuckle. Arbutus unedo, cotton, poplar, chestnut, 
alfalfa, grape, hop, beet, salsify, turnip, parsnip, lettuce, and 
willow. 
^ Some cross-inoculate less readily than others, but, in 
general, the monotonous morphology, the cultural uniformi¬ 
ties, and the ready cross-inoculability (daisy, peach, hop, 
grape, poplar, alfalfa), point to one polymorphic species 
rather than to several distinct species, but further studies 
should be made. 
The galls also invite various parasites—nematodes, 
fungous root rot, fire blight of apple and pear, etc., and 
some of these are able to cause great damage. 
We have not been able to distinguish etiologically be¬ 
tween hard galls and soft galls. Even the hardest crown- 
galls are due to bacteria which closely resemble those found 
in the softest. 
The size of the tumor, other things being equal, depends 
on how rapidly the plants are growing, i. e., the state of 
nutrition. Actively growing plants usually developed large 
tumors when inoculated, and slow-growing plants none at 
all or small ones; but, as in apple, small slow-growing galls 
may finally become large. This long-continued growth 
would not be possible if there were not a very nearly even 
balance between the stimulus of the parasite and the 
response of the host. 
The apple hairy-root, hitherto a disease of unknown 
origin and supposed to be noninfectious, has been shown to 
be due to bacteria which culturally and morphologically 
differ, if at all, only slightly from the crown-gall organisms. 
Typical hairy-root has been produced on sound apple 
seedlings by pure-culture inoculations, and in the same way 
on sugar beet both galls and hairy-roots have been obtained. 
The disease is one which progresses slowly, stunting the 
plant first and finally destroying it, unless removed by 
extirpation or by the development of increased resistance on 
the part of the plant. 
The continuation of rigid State inspection with rejection 
of diseased nursery stock is recommended.’’ 
METHODS OF DEALING WITH THE DISEASE AND RECOM¬ 
MENDATIONS TO NURSERYMEN 
On this subject the authors have the following to say; 
“Up to this time the best method of dealing with this 
disease remains the old one of strict inspection of nursery 
stock and the condemnation of all trees and shrubs found 
