BOTANICAL GAZETTE. 343 
such arrangements had been made, several botanists gave up the 
trip entirely and collected in the vicinity of Ann Arbor, while 
those who did go would gladly have left the boat at any one of 
kn points, had it been possible, and been picked up on the 
retu 
meriting much trouble or attention. If this is the proper ex- 
planation, the registration of over a fifth of the total aitendance 
as members of the Botanical Club must have brought about a 
change of opinion before the meeting was over. 
Proof that Bacteria are the Direct Cause of the Disease in Trees 
Known as Pear Blight.’ 
BY J. C. ARTHUR. 
It has now been five years since Professor Burrill brought 
the subject of pear blight before this Association and announe 
that it was due to bacteria. Previous to that time no instance of 
bacteria acting the réle of vegetable parasites had been known, and 
important one, opening the 
t the disease may be 
roducing a drop of an 
f the diseased tissues 
‘Read before the American Association for the Advancement of Science, August, 1885. 
