124 INTERRELATIONS OF PLANTS AND ANIMALS 



3. RESULTS OF GROWTH 



Observations. 1. Loosely stopper a bottle containing grow- 

 ing yeast. Draw out some of the gas above the yeast by 

 means of a large bnlb pipette and bubble the gas through lime- 

 water. Result ? 



2. Show how, when yeast is put into dough, the conditions 

 of its growth are present. 



3. What gas must be set free in the dough ? 



4. What happens when yeast acts in sugar ? 

 Note. The name of this process is fermentation. 

 Conclusions. 1. What causes bread to rise ? 



2. Why does bread " fall " if not baked soon after it has 

 risen ? 



3. Why set the dough in a warm place for rising ? 



b. Some Economic Relations of Other Fungi 



Observation. Tabulate the information called for in the 

 following table, so far as you are able : 



FUNGI 



Questions 



1. What becomes of the alcohol produced by using yeast in 

 dough ? 



2. Explain the use of yeast in bread making. 



