160 



BOTANY 



Experiment with mold on bread; ^, in a living 

 room; B, in an ice-box; C, above the stove in a 

 kitchen. 



pose both jars to the air of the living room or kitchen for five minutes. 

 Then cover both jars and plunge one into boiling water for a few minutes. 

 Now place the jars side by side in a moderately warm room for two or three 

 days. In which jar does growth appear first? Do both jars have like 



growth of mold in the given 

 period of time ? 



Other experiments may be 

 performed to show the rela- 

 tion of the growth of mold to 

 light, to different degrees of 

 moisture and to different tem- 

 peratures. Why do things 

 get moldy in a damp locality 

 quicker than in a dry one ? 

 How Avould you account for 

 the growth of mold inside of 

 a jar of preserves or jelly? 

 Can you determine by experi- 

 ment whether black mold uses 

 oxygen in its growth? 



Directions for Growth of 

 Mold. — Bread mold may be 

 conveniently grown for laboratory use in small shallow dishes (Syracuse watch 

 glasses, Petri dishes, or butter chips) . If bread is exposed to the air for a few 

 minutes and then left in the covered dishes for a day or two, with a bit of wet 

 sponge or blotting paper in the dish to keep the air moist, a good supply 

 of mold may be obtained in a convenient dish for observational purposes.^ 



Observations on Mold. — Examine the tangled mass of threads which 

 cover the bread. This is called the mycelium, each thread being called a 

 hypha. How do the hyphae appear to be attached to the bread? Many of 

 the hyphse are prolonged into tiny upright threads, bearing at the top a little 

 ball. With the low power of the microscope the structure of a sporangium 

 may be made out. The dark-colored 

 ones are full of ripe spores, which 

 may be seen by lightly tapping the 

 cover slip over the slide. How do 

 the spores normally get out of the 

 sporangium? Try to find some 

 young sporangia and note the differ- 

 ences in size and color between them 

 and the older ones. Draw a series 

 of sporangia as seen under the low 

 power. 



This method of the produc- 

 tion of spores is evidently asex- 

 ual. These spores, if grown 

 under favorable conditions, will 



■--'••lyilllVi'nii"' 



Bread mold; r, rhizoids; s, sporangium. 



produce more mycelia, which in turn bear sporangia. It has been 

 found, however, that at some time during the life of the mold 

 another method of reproduction is likely to occur. 



' See Hunter and Valentine, Manual, page 83. 



