1182 Pear Blight and its Cause. [ December, 
storm following hot and damp weather. Its true nature, so differ- 
ent from these conceptions, has been learned by inoculating 
healthy limbs with germs from an affected tree and closely 
watching the progress of the disease through its whole course: 
from inception to the death of the limb. The inoculation is made 
by puncturing the limb and applying some of the gummy exuda- 
tion, or, better, a drop from a watery solution of it, or from water 
in which some diseased tissue has been sliced. If this be done 
in July and the inoculation be made in a young and tender shoot, 
the tissues near the wound will show discoloration in about a 
week, and in the course of a-week longer the leaves and end of 
the shoot become blackened and dead. Let it be noticed that at 
the most favorable season for development it requires some two 
weeks from the time of the attack to enable the disease to gather 
sufficient headway to be conspicuous; for no observer is likely 
to detect the change in the color of the bark before the dying 
leaves have fixed his attention, unless he knows an artificial inoc- 
ulation has been performed. This sufficiently disposes of the 
supposition that the disease is sudden in its action; still more 
marked proof will be adduced later, showing that in natural 
course it is slower yet. Over two hundred recorded inoculations 
have been made, and from these we learn that the disease makes 
the most rapid progress in the newest and most succulent tissues ; 
and the nearer to a vigorously growing bud an inoculation is 
made, the more likely it is to succeed. In fact, it was soon 
found that no result was likely to follow an inoculation in wood 
a year or more old. This suggested the inoculation of growing 
fruit; the results were most surprising, for the tender parenchy- 
matous tissues were entirely broken down into a creamy fluid, 
-which now and then escaped at the wound made in inoculating 
and dripped upon the ground. 
| Repeated. attempts to convey dhe doere by lnpculating the 
, eaves resulted in failure, except a partial success when very 
young leaves were tried. It is noticeable that the leaves are the 
ast to succumb to the disease; they will remain green for days 
or € en weeks after the bark at that point has become brown and 
sad. Bacteria cannot be found swarming in the leaves as in the 
ad wood; the conditions do not seem favorable for their 
The c clusion i is inevitable that the death of the 
ranch is chiefly due to the cutting off of 
