EXERCISE 82 

 BLUE MOLD, OR BLUE MILDEW 



Materials. The cultures prepared in the preceding exercises; 

 hand lens ; if possible, microscope, slides, and covers. 



Directions for work. Study the colonies and determine the 

 manner of increase in size and the differences between the 

 older and younger parts of the colonies. If you have colonies 

 in a transparent medium, such as the gelatin, note the growth 

 of the colony in the medium. If it is possible to view a colony 

 on gelatin through a low-power objective (one-inch or two- 

 inch) of the microscope, it will be possible to secure a very 

 good idea of the whole plant in its natural relations. 



What evidence, direct or indirect, do you have that the 

 mold is drawing food from the substance upon which it grows ? 

 Will it grow in the dark ? Does it have any observable effect 

 on the substance upon which it grows ? 



Blue vitriol (copper sulphate, CuSO 4 ) is commonly used in 

 the making of fungicides. Place a small piece of a crystal, not 

 much larger than a pinhead, near a growing colony of blue 

 mold and note the result after several days. Does it have a 

 fungicidal (fungus-destroying) action ? Do the same with a 

 drop of lime-sulphur mixture if you can secure it. 



If compound microscopes are available, very carefully pick 

 up a few fibers of the mold and mount in a drop of alcohol on 

 a slide. Add water to replace evaporation of the alcohol. 

 Examine the character of the hyphge, the branching, and the 

 manner of forming spores. Record the principal facts in a 

 drawing. Compare with illustrations in books to discover the 

 name. 



References 



BERGEN and CALDWELL. Practical Botany, pp. 231, 232. 

 BERGEN and CALDWELL. Introduction to Botany, p. 245. 



[104] 



