DISEASES OF THE QUINCE. 83 
roots or mycelium, or live within it asa saprophyte. A 
healthy tree possesses sufficient vigor to resist the attacks 
of diseases, and may grow on successfully when a feeble tree 
would be destroyed. A fungus may be so concealed in 
the tissues of a plant on which it is thriving, that its 
presence will only be known by the mycelium cropping 
out with spores on the surface. 
1. QuINCE Biicutr.—It seems to be well established 
that this disease, also called fire blight and twig blight, 
is the same as the pear blight in the pear and the apple 
blight in the apple. The disease has been produced in the 
June-berry (Amelanchier Canadensis), the English Haw- 
thorn (Crategus Oxyecantha), and the Evergreen Thorn 
(Crategus Pyracantha), by inoculation, and may prob- 
ably be so produced in any member of this family of trees. 
Every part of the tree above ground is subject to its 
attacks. It may extend only to tender twigs, or it may 
entirely destroy the tree. ‘The presence of this disease 
may be recognized by the granular appearance of the 
bark on the tender twigs, accompanied by the exuding 
of a gummy substance, of a peculiar odor, quite sticky to 
the fingers in the morning after a heavy dew, and drying 
up so as to glisten in the sun, when it forms into granu- 
lations on the discolored bark. 'This gummy substance, 
as scen through a microscope, resembles filamentous 
threads, each being strung with sacks of bacteria, ready 
to burst and scatter their infinitesimal germs by the aid 
of the lightest breeze, or to be washed to the earth by 
summer showers. The author was aided in examining 
this gum from a blighted twig by Prof. J. B. Ellis, 
author of ‘‘ North American Fungi,” and it was found 
that so little as could be picked up on the point of a pen- 
knife, put into a drop of water on the glass slide of his 
microscope, revealed an innumerable number of spores, 
or bacteria, too small to be described. ‘The stomata of 
a leaf, examined at the same time, was large enough to 
