DISEASES OF THE QUINCE. 83 



roots or mycelium, or live within it as a 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 BLIGHT. 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 (AmelanMer Canadensis), the English Haw- 

 thorn (Cratcegus Oxycaniha], and the Evergreen Thorn 

 (Cratcegus 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 seen 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 



