BOTANICAL GAZETTE. 345 
the other cultures of the series was successively made with a 
small drop of the one preceding. From the last culture a drop 
was transferred to a puncture ina ripe Bartlett pear. In bot 
cases the pears were soon filled with the disease. They did not 
turn brown about the wound, as is the more usual way, but first 
indicated the presence of the disease by beginning to shrivel, 
which occurred in one case in nine days after inoculation, and in 
the other in ten days. Upon cutting the pears open the softer 
tissues were found broken down and liquefied, and a milky viscid 
juice ran out, showing that the disease had taken thorough pos- 
session, 
y this means of fractional culture the juices accompanying 
the bacteria first introduced were so much diluted in the trans- 
fers to succeeding cultures that the final drop used to inoculate 
the pear was practically free of them, and to the bacteria only, 
supplied by continued growth and multiplication, can be ascribed 
the last result. 
4 porous earthenware vessel, such as used for small electric bat- 
teries, and an unripe Bartlett pear inoculated with the filtrate 
se. In this case 
two unripe Bartlett pears were inoculated with the unfiltered in- 
bacteria accompanying the disease of trees known as pear blight 
€n fully isolated will produce the disease, while the juices in 
