REPRODUCTION BY SPORE FORMATION 251 



elementary science may be used to show that these bubbles are 

 carbon dioxide. The alcohol may be recognized by the odor. 

 The process of fermentation always accompanies the reproduction 

 of yeast plants. Since the yeasts are dependent upon nonliving 

 organic material for food, they are called saprophytes. 



Problem. Spore formation in mold. 



Place a piece of bread on several thicknesses of well-moistened filter paper 

 or blotting paper on a plate. Expose the bread to the air, sprinkle it with dust, 

 or infect it with mold spores. Cover with an inverted glass dish that is raised 

 up on one side to admit a little air. Be sure the bread does not dry. Moisture, 

 a limited amount of air, warmth, and organic material are necessary for the 

 growth of molds. The hairy growth that appears on the bread is one type of 

 mold, the bread mold. It takes from one to four days to grow these plants. 



Mount a minute amount of the hairy structure under the low power of the 

 microscope. 



I. Describe the shape and color of the cells of the mold. 



A. Are there any cross walls to the cells? 



B. Do the cells branch or not ? These cells are known as hyphae. 



C. The mat of cells is known as the mycelium. The threads that are 

 actively feeding and growing are called the vegetative hyphae. 



II. Try to mount a piece of mold that was actually embedded in the bread. 

 A. The anchoring rootlike structures are called rhizoids. By means of 



these, the mold gives out enzymes that dissolve some of the bread. The 

 dissolved bread is then absorbed as food by the mold. 



I. Observe the structure of the niold and explain why it is prob- 

 ably a saprophyte. 



II. Discuss the difference between the mold and Spirogyra in types 

 of nutrition ? 



III. When the mold is three or four days old, note the tiny dark bodies that 

 appear. Mount a bit of the mold structure, including several of these bodies, 

 under the low power of the microscope. Be sure not to take too great a mass 

 of material. 



A. Describe the structure of one of the small black bodies. This is a 

 sporangium. 



B. Describe the structure that holds the sporangium. This is a repro- 

 ductive hypha. 



C. Locate a broken sporangium. Describe the structures escaping 



