56 STATE BOARD OF AGRICULTURE. 



ium rapidly penetrates, spreading to all parts of its victim, soon causing 

 the death of the host plant. And, in still other cases, the fungus may 

 enter the host plant when it is in the seedling stage, developing along 

 with the host to appear in the fruit in its mature form. 



After the n\ycelium has become well established, upon or in the tis- 

 sues of its host, it usually begins the production of spores — the 

 reproductive bodies of the fungus. Spores may form in several w^ys, 

 the simplest being that in which they form on the ends or sides of 

 little branches of the mycelium, these branches being pushed out 

 through the surface of the affected portion. 



A great many parasitic fungi produce two or more kinds of spores. 

 One kind is produced in great abundance during the earlier part of the 

 growing season and is capable of germinating at once, thus serving to 

 distribute the fungus to healthy plants. The second spore form usually 

 appears later in the season, and remains dormant through the winter 

 to germinate in the spring, thus starting the fungus Avhen other plants 

 are beginning a new growth. The former have been termed summer 

 spores, the latter resting, or winter spores. 



Spores are usually produced in enormous numbers. Thus the space 

 occupied by the head of a common pin could, if packed full of spores 

 like those of some common puffballs, contain about eight millions of 

 these minute bodies; while the common blue mould, which often appears 

 on old cheese or decaying fruit, produces spores so small that more 

 than fifteen millions of them could be placed in the same space. Their 

 minute size enables them to float readily in the air, or to be carried on the 

 bodies of insects or the feet of birds. Thus it is not to be Avondered at 

 that fungi appear so quickly and readily whenever the conditions are 

 suitable for the spores to germinate. 



When these spores fall into a drop of water or on a moist surface 

 they may germinate, often very rapidly, and, if the surface hajjpens 

 to be that of a plant suitable for the sustenance of the fungus,- it may set 

 up the disease at this point. 



Prevention of parasitic fungous diseases therefore resolves itself into 

 the matter of preventing the germination of these spores in contact 

 with our plants. Moreover, the careful destruction of diseased parts 

 of plants, especially when they contain resting spores, may also serve 

 to decrease the liability of attacks. The use of spraying mixtures to 

 protect plants from the attacks of fungous diseases is familiar to all of 

 you. These mixtures, the most important of which contain some salt 

 of copper, possess the power of killing the spores of fungi with which they 

 come in contact. Consequently when the leaves and tender parts of our 

 plants are coated with a thin layer of such a material, the spores are 

 unable to germinate and infect such plants. Spraying, however, must 

 be done thoroughly in order to be of much value. 



Another important means of combatting fungous diseases of plants is 

 based on the fact that some varieties, or races, and even individual 

 plants exhibit a greater degree of immunity from the attack of parasitic 

 fungi than others. Hence it has been possible in some cases by selection 

 and breeding to produce strains, races and varieties which are capable 

 of resisting fungous parasites to a considerable degree. 



The following fungi are all old offenders and are of interest to every 

 person engaged in the growing of plants on the farm : 



