1906] SMITH—A BACTERIAL DISEASE OF OLEANDER 303 
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formation of callus tissue and hence an increase in the size of the 
knot. : 
These large knot-like growths of the olive may be found on the 
leaves, branches, and trunks, few in number or in great abundance. 
They must not be confused with those caused by insects, and they 
are also distinct from the enlargements formed on the roots of the 
Leguminosae by bacteria. Badly diseased trees show scant foliage, 
limited growth, and occasional dead branches. 
The cultural characteristics of the olive knot organism have been 
studied by Savastano (5) and seem to agree quite well with those 
observed during this study. The following is a portion of the trans- 
lation of SavasTANo’s account of the disease as published by 
PIERCE (7): 
This microorganism is a bacillus of medium size; length three to four times 
its width; it is isolated, but is sometimes joined into chains; the extremities are 
slightly rounded off. In drops of bouillon it has a distinct movement. The 
colony has a variable form, from round to oval, with a well-defined margin. In 
the beginning it is uniformly pointed; later it forms one or two peripheral cir- 
cles. It is whitish by reflected light, cedar color by transmitted light. The 
bacillus lives well in ordinary culture media (bouillon, potato, gelatin, agar). 
The culture has a relatively long life; cultures made in March were still living 
in June. In short, degeneration begins in about three months. On potato it 
lives very well and develops rapidly; the colonies are at first like so many round 
dots, translucent straw color, which, as they develop, form on the surface of the 
potato a uniform stratum, translucent, and of a deeper color. The bacillus 
acquires greater dimensions. On gelatin plates it lives very well, with characters 
and forms as above indicated. In the tubes of gelatin (a becco) the culture 
presents the appearance of a uniform stratum, whitish, the margin finely bilobed, 
reminding one of the margin of a leaf, the whole culture taking the form of a 
Spatulate leaf. It is slightly dichroic. In tubes of agar (a becco) the culture 
is identical with the preceding, the margin is less bilobed. The culture by needle 
in gelatin presents a uniform, transparent, finely pointed appearance. On the 
Surface of the meniscus the form is irregularly rounded, with a finely lobed margin, 
as in the preceding. 
In the study of the present disease, the organism was first isolated 
from the oleander in the manner described below. Inoculations 
were then made on the oleander and olive. Positive results were 
obtained in all cases, No effort was made to try inoculations on 
other Plants. Savasrano ( 5), however, failed to make successful 
Moculation with the olive knot organisms on peach, plum, apricot, 
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