CRYPTOGAMS 241 



Method. Expose the dishes in various places for two 

 or three minutes. Then cover them and set them away for 

 the molds to develop. 



Make the exposures in different places, as cellar, pantry, 

 parlor, etc. Make some exposures out of doors and others 

 in the house. 



After three or four days, what results are to be seen ? 



Conclusion. What does this show concerning the prev- 

 alence of mold spores in the air ? 



206. MOLDS 



Object. To show that there are mold spores in dust. 

 Apparatus. Petri dishes as before. 



Method. Over one Petri dish shake a dry dusting 

 cloth or feather duster. Over another, shake a damp dust 

 cloth. Over a third shake a rug. Into a fourth drop 

 a bit of dirt scraped from a crack in the floor. 



Close all the preparations and set them away for develop- 

 ment of molds. After three or four days note the result. 



Conclusion. What may be inferred as to the occurrence 

 of mold spores in dust? From your experiment which is 

 better to use, a dry or a damp dust cloth? Why? 



207. MOLDS 



Object. To learn some of the conditions favorable to 

 growth of molds. 



1. Moisture. Place a piece of wet bread and a piece of 

 dry bread side by side on a plate and cover them with a bell 

 jar. After a week study the preparations. On which one 

 does mold develop best? Inference? 



2. Temperature. Prepare three Petri dish cultures. Sow 



EXP. EOT. 16 



