210 CIVIC BIOLOGY 



three may collect specimens showing all stages of infestation of leaves 

 and tubers for actual demonstration, make pictures of the fungus and 

 diagrams showing how it attacks the potato plant, and finally give the 

 best methods for its control. 



Infection. The process of infection is as simple as that of 

 planting seeds in a garden plot and raising the particular 

 kind of flower or vegetable or of inoculating mold spores in 

 any sort of food cultures. The spores of the parasite germi- 

 nate in contact with their host plant, and the hyphse enter 

 through wounds or stomata or actually eat their way through 

 the cells of the surface. 



In order to develop perfectly clear ideas, perform all sorts of in- 

 oculation experiments with fungi that happen to be available. Let 

 members of the class use different kinds and demonstrate methods 

 and results. Use any of the following, or others of local importance. 

 Inoculate by touching point of pin to spores and pricking surface : 

 A potato tuber or leaf with spores of blight or scab ; 

 Seedlings of corn, or other grains, with smuts or rusts ; 

 Lettuce plants with spores of " drop " (Sclerotinia libertiana) if 



locally important ; 

 An apple with spores of bitter rot ; 

 A plum, peach, or cherry with spores of brown rot (Sclerotinia 



fructigena), always at hand everywhere ; 



Bean seedlings with germs of bacterial blight (Pseudomonas 

 phaseoli) or spores of pod spot or anthracnose (Colletotrichum 

 lindemuthianuni). 



In these days of quack nostrums, illogical thinking, and even 

 hysterical denial of cause and effect in matters of disease, these 

 lessons with plants, which are not subject to fears and perverted 

 mentality, may help to keep us sane. 



Wound infection of trees. A search through the orchard 

 or wood lot is all too likely to show trees with mushrooms 

 of different kinds polypori, hydnums, oyster and honey 

 mushrooms growing upon trunks or roots. Inspection 

 seldom fails to reveal the wound in the bark through which 

 the fungus entered the wood. It is probable that these 



