THE PATHOGENIC NATURE OF MOLDS 113 



EXERCISE 39. TO DEMONSTRATE THE PATHOGENIC 

 NATURE OF MOLDS 



Apparatus. One deep culture dish; one perfect fruit 

 the same as that from which the mold was isolated, or 

 any fruit which is the natural habitat of the mold. 



Cultures. Pure culture of a mold isolated, from a fruit. 



Method. 1. Make small circles on opposite sides of 

 the fruit with the wax pencil. 



2. Puncture the center of one circle with a sterile 

 platinum needle. 



3. Then with needle contaminated with the mold spores 

 inoculate the circle on the opposite side by puncturing as 

 in 2. 



4. Place at about 25 C. and observe from day to day 

 for two weeks. 



5. How do fruits usually become contaminated with 

 molds? What preventive measures would you suggest? 



6. What is a perfect fruit from the bacteriological 

 standpoint? From the horticultural standpoint? May 

 these view-points differ? If so, how? What other fruits 

 would be susceptible theoretically to the mold you used? 

 Why? 



What other types of microorganisms may be path- 

 ogenic to fruits? 



7. State in full the results obtained, with any con- 

 clusions that may be drawn, and point out the practical 

 application which may be made. 



REFERENCES 



MARSHALL: Microbiology, p. 513. 



SMITH, ERWIN F.: Bacteria in Relation to Plant Diseases, Vol. I, p. 202, 



Plates 29, 30 and 31. 

 SMITH, ERWIN F.: Bacteria in Relation to Plant Diseases, Vol. II, 



Fig. 13, pp. 60 and 174-181. 



