ELEVENTH ANNUAL MEETING. i37 



Now we pass to the third form of plant parasite, the thread- 

 Uke fungus. This form is probably the most common, but 

 in all cases the great difficulty in fighting the various forms 

 of disease-producing organisms lies in the fact that in most 

 cases they are so small that we cannot see them with the naked 

 eye. A great many of our insect pests are beautifully illus- 

 trated and described and, being large enough to be seen with 

 the naked eye, become familiar objects, and in them there is 

 something tangible to combat. One fact, however, should be 

 strongly emphasized in this connection, viz., that these disease- 

 producing organisms are just as real, and just as definite in 

 their structure, as if we could see them with the unaided eye. 

 If we examine closely one of these fungi of the third class, 

 we shall find that it is made up of one or more thread-like 

 bodies which are hollow, and which are sometimes divided by 

 cross walls into compartments. These organisms are really 

 plants of a very peculiar structure and possess peculiar methods 

 of reproducing themselves. The reproducing bodies that are 

 formed are called spores. These bodies differ in appearance 

 in dififerent fungi, but their function is always the same, viz., 

 the reproduction of their kind. Wherever these little bodies 

 find a place where the conditions are favorable, new threads 

 will be sent out, and a new fungus plant will be produced. 

 These reproducing bodies are usually too small to be seen with 

 the naked eye and are easily carried about by the wind or upon 

 the feet of insects. Many of these spores are protected through 

 unfavorable seasons by a provision of nature, and they are 

 thus enabled to live through the winter or through seasons 

 of excessive dryness. As it is, a large number of spores are 

 destroyed, but enough ■survive to perpetuate the species and 

 often to cause untold damage.* 



The thread-like structures that develop from the spores force 

 their way into the tissues of the plants upon which they grow 

 and rob them of their nutritive substances. It is in this way 

 that these parasitic plants obtain their food, and at the same 

 time they impart to their hosts more or less poisonous material. 



The bitter rot of the apple, for example, is produced by one 



*Slides were exhibited, showing methods of spore formation, the 

 manner in which the fungus is produced from the spore and the way 

 it feeds upon its host plant. 



