INTERRELATIONS OF PLANTS AND ANIMALS 137 



d. A Hay Infusion (Another Food Relation) 



Observations. 1. Make a hay infusion as in the preceding 

 problem. Let it stand a few days. What is the change in 

 color ? Appearance ? Odor ? 



2. Is there a scum on top ? If so, what does it indicate ? 



Conclusions. 1. What is a tea infusion? Similarly, what 

 is a hay infusion? 



2. How do you think bacteria came to be in the hay infu- 

 sion ? 



3. Where did the bacteria come from? 



4. On what may the bacteria feed ? What is the result of 

 their action ? 



Observations. 1. With a bulb pipette put a small drop 

 from the scum on a glass slide and examine it with a low 

 power of the microscope. 



2. Do you see small one-celled animals moving about ? 



Note. If corn meal is scattered on the scum, any small 

 animals present, as paramcecia, will congregate about the meal 

 to feed. Dipping near the bit of meal will then more surely 

 result in getting numbers of paramoecia or other one-celled 

 animals. 



Conclusions. 1. Where must the one-celled animals have 

 come from ? 



Note. Grass for hay is commonly grown near pools or 

 wet places that dry up about haying time. These places 

 practically always contain one-celled animals (Protozoa) that 

 encyst themselves as they dry up, much as the resting spores 

 of spirogyra or molds do; when this happens, they are blown 

 about with the dust. 



2. How do these encysted forms resemble seeds ? 



3. What causes seeds to awaken? What then likely caused 

 these little dormant one-celled animals to awaken in the infu- 

 sion ? 



4. Write a paragraph telling just why hay is used in the 

 above manner in order to get one-celled animals for study. 



