APPENDIX 273 



a beaker of boiling water and allow the water to boil briskly for half 

 an hour, after which the gelatin is to be poured into a petri dish and 

 treated like that in the first tube. Set both dishes aside for mold 

 growth, and examine at intervals for several days, noticing whether 

 molds develop in both dishes or only in the first. If they grow in 

 both, note the relative abundance in the two dishes. 



15. Effect of Low Temperatures. Prepare two plates of hardened 

 gelatin and sow mold spores upon the surface of each. Leave one in 

 the ordinary room temperature and place the other in an ice chest or 

 some other place where the temperature is low. Compare day by day, 

 and determine the effect of low temperatures in checking or stopping 

 mold growth. Do any molds grow upon the dish placed in the ice 

 chest? 



1 6. Effect of Air Currents. Moisten a slice of bread and sow mold 

 spores "upon it, or allow it to mold spontaneously under a bell glass. 

 After it shows a luxuriant growth of mold remove the bell glass and 

 leave it exposed to the currents of the air. Notice how the growth 

 of the mold ceases and the delicate mycelium flattens down close to 

 the bread. 



17. Molds in Cheese. Obtain a bit of Roquefort cheese. Cut it 

 open and remove a bit of the green mass in the middle by means of 

 a knife point or a platinum wire. Sow this substance upon the sur- 

 face of a dish of hardened gelatin and set aside for growth. After 

 two or three days the molds will begin to develop and may be studied 

 with a microscope. When they begin to produce fruit they should, 

 if possible, be studied sufficiently to determine the species. This 

 species of mold is figured in Chapter II and should be easily identified. 



18. Decay of Fruit (a). Place in a jar a number of apples that have 

 been bruised or cut, packing them in rather tightly. Scatter in the 

 jar some spores of the common blue mold which will usually be found 

 on some of the petri dishes already prepared. Close the jar and set 

 aside. Prepare a second jar with some whole clean apples and treat 

 in the same way. Compare the two jars for a week or two to see if 

 decay makes its appearance in either or in both of the jars. Does 

 bruising hasten the decay of the fruit? 



19. Decay of Fruit (). Make a cut through the skin of an apple 

 with a knife blade that has been previously dipped into the midst of 



