88 
BACTERIA IN PLANT DISEASE. 
spots occur on the leaves, which showed no trace of insects or 
fungi. That “ the peculiar appearance and location of these spots 
led to a careful study of the same, which resulted in finding 
bacteria-like bodies in large numbers within the chlorophyllose 
cells of the spongy parenchyma immediately surrounding the 
spiral vessels supplying that region. After a long series of 
observations made on material from various portions of the 
diseased districts, which in no case failed to disclose the diseased 
vines as swarming with these bodies in all portions where sap had 
a ready flow, he believed it proper to undertake a series of experi- 
ments to determine if these bodies always present bore any relation 
to the disease as a whole. He had little doubt that they were 
micro-organisms, and gave to the local spotting of the leaves their 
characteristically sharp outline. Cultures from various parts of 
the vine were made in agar-agar and other media. Three sorts 
of bacteria were found with enough constancy to warrant further 
study, but he had not so far been able to determine whether any 
of these were the cause of the disease. In view of the fact that 
several Italian students have for years claimed that an Italian 
disease of similar characteristics is caused by bacteria, it is proper 
the matter should be decided if possible.”* 
It is established then, beyond doubt, that bacteria inhabit the 
tissues of plants in great numbers, that they appear to be of 
kinds peculiar to those plants, and may, or may not, be the cause 
of some of the plant diseases. To carry on the subject still 
further we must refer to a series of investigations on a disease of 
melons, and, by the results of these investigations, exhibit a very 
strong presumption that microbes are the cause of some diseases 
of plants. 
“ The attacked vines varied somewhat in their appearance, but 
generally there is a decay of the stem in proximity to the root, 
and then the whole plant wilts and fails to grow. Sometimes one 
or more leaves will fall to the ground, and rot away, before the 
balance of the plant is seemingly affected.” 
Dr. Byron Halsted reportsf that “ a microscopical examination 
of the decaying stems, leaves, and fruit showed that the decom- 
posing tissues were teeming with bacteria. Inoculations of healthy 
fruits were made in the usual way, taking the germs from the 
centre of freshly-decaying cucumbers. It was found that with no 
other fungus present these germs were abundantly able to introduce 
a rapid decay into cucumbers, melons, and squashes. Cucumbers 
seem to be the favourite, and in them the decay is the most rapid. 
It will run from one end to the other, through the succulent centre 
of a four-inch fruit, in a single day. 
“ The next step in the study was the application of these germs 
to healthy plants in the field. When the inoculation was made 
near the end of a vine the latter rotted away in from three to four 
days, and when nearer the base a longer time was required, but in 
* Report’for 1859, p. 427. 
f “Botanical Gazette,” Nov., 1891. 
