1906] SMITH—A BACTERIAL DISEASE OF OLEANDER 305 
It required considerable time in the writer’s experiments for the 
disease to develop, though in a month’s time the first indication of 
tissue enlargement could be observed. This continued to increase 
until on the olive quite a knot was formed in two month’s time 
(fig. 3). Often the infection did not produce such a large knot as indi- 
cated in fig. 3, but smaller swellings of the tissue. In this inoculation 
work agar cultures, 48 hours old, were used, except on one occasion 
when a bouillon culture was tried. Either gave equally satisfactory 
results, The visible effects of the inoculations showed sooner on the 
oleander, but their size and the rapidity of knot-formation seems to 
depend upon the rapidity with which the plant is growing, as has been 
before observed by SavasTANo (4) in his study of the olive knot. The 
organism grows on both the stem and the leaves. In one experi- 
ment a leaf of an oleander near the top of the plant was inoculated 
on the midvein; this inoculation grew well, and from it secondary 
natural infections resulted on the stem. It was not difficult to trace 
the new infections on the stem to the very base of the petiole of the 
diseased leaf. Infection (fig. 4) took place probably through the 
stomata and lenticels. Checks were used by making punctures with 
a sterile needle, but these gave no knot formations. 
The lesions and growth on the hosts were quite different. On the 
Oleander at first there was a slight enlargement of the tissue that 
became somewhat rounded at the point of infection. After a time, 
as the new growth continued, there was a splitting of the epidermis 
in a longitudinal direction, forming a cleft (fig. 4). After this a 
spongy growth formed, which is rather dark in color and contains 
humerous small colonies of the bacteria. On the olive there was the 
same enlargement of the tissue as in the oleander, but the formation 
of the new growth was much more rapid, regular knots being soon 
formed by the growing out of the new tissue. This took place in 
the olive rapidly, while in the oleander it was only in the advanced 
Stages that this new callus tissue grew into a knot-like formation. 
he knots on the olive agreed in appearance with specimens of the 
typical knots as it occurs in California, and with the illustration as 
given by Prerce ( 7), Broretti (8), and ERwin SMITH (9). 
The original cultures were made from the diseased tissue of the 
oleander by first cutting away the outside tissue with a scapel, steri- 
