438 G. P. DARNELL-SMITH. 
In tobacco plants from the neighbourhood of the dis- 
coloured tissue, I have obtained smears full of bacteria, 
and have obtained cultures of them from various parts of 
the plant. They exist in such numbers that there seems. 
good reason to suppose that they are the cause of the dis- 
coloration and the diseased condition. A tobacco plant. 
has bast inside and outside the ring of wood; in the neigh- 
bourhood of this bast the bacteria are very numerous. The 
wood of a diseased stem snaps easily, and often shows little 
splits and cavities filled with a dark material. A plant 
affected by bacteria shows, when young, a peculiar appear- 
ance. The stem, immediately above the roots, swells and | 
becomes tumid, sometimes almost bulbous. The stem may 
be abnormally swollen for two inchesormore. If the plant 
remains short and swollen, it is regarded as being worthless. 
for planting out, but if, as sometimes happens, it begins 
to lengthen and lose its swollen appearance, it may be 
worth transplanting, though it never fully recovers. . 
Tyloses are very frequently to be observed in the vascular 
tissue of the swollen plants, and in the vascular tissue of 
older diseased plants. The production of swellings and 
tyloses is rather a commom symptom of bacterial infection, 
and it was this that first led me to suspect bacterial 
infection. 
Erwin Smith® to whose recent monumental work on 
Bacteria in relation to Plant Diseases I shall have fre- 
quently to refer, states :— 
‘“‘In hypertrophied tissues the individual cells are larger than 
normal. Usually both hyperplasia and hypertrophy occur in the 
same growth, e.g. in olive-tubercle. Good examples of hyper- 
trophied cells occur also in root nodules of Leguminose. Here 
their volume may become many times that of the normal cell. Dr. 
Hunger pointed out that tyloses are very common in the vessels. 
of plants attacked by Bact. solanacearum, and ascribed their 
formation to the presence of the bacteria. Of the correctness of 
