1896.] The Bacterial Diseases of Plants : 725 
reach full size, and especially as they approach maturity, those 
which are most affected can be told at a glance by the altered 
appearance of the leaves. The healthy beet leaf has a decid- 
edly flat, uniform surface, while the diseased leaf is puffed out ` 
between the veins in little blister-like areas, giving the general 
appearance of the surface of a Savoy cabbage leaf. Diseased 
plants are necessarily less vigorous than healthy ones, and the 
fact is made apparent to the eye as the season advances, by the 
leaves becoming paler and smaller, and the outer ones dying 
away faster than upon healthy plants. All these indications 
taken together, most reliance being placed upon the crinkled 
surface, will enable one to select much diseased plants as they 
are growing in the field, with considerable certainty. But 
some roots not showing the foliage characteristics will also be 
found to be affected. 
“ Upon cutting across a root the most bonitans indication of 
the malady is a greater prominence of the fibres which form 
the concentric rings. In well-marked cases each microscopic 
bundle shows a dark dot, the circles of dots growing more dis- 
tinct on exposure to the air. In less pronounced cases the 
woody fibres are merely yellowish, or even quite colorless, but 
more prominent after being exposed to the air for awhile than 
normal tissues. Furthermore, the diseased root is rather soft 
and tough, and of a yellowish-white color, while a healthy 
root is firm, somewhat brittle, and in color a clean white. 
It has also been found that diseased roots are lighterin weight 
than healthy ones.” They also contain less sugar. The reduc- 
tion in all cases being considerable, and in some cases amount- 
ing to nearly 50 per cent. This is “presumably due to the 
presence of the bacteria.” 
In a foot-note it is stated that the circles of dark dots are 
found in all sugar beets. “And yet the greater prominence 
which these dark spots assume on account of the disease, make 
them one of the most effective indications of its presence.” 
(4) Pathological Histology. — A microscopic examination 
showed the bacteria “throughout all parts of the root.” “So 
far as observed the disease rarely or never breaks down the tis- 
sues or kills the plant.” 
