266 



FOUNDATIONS OF BOTANY 



fruiting cells (basidia) wliich project at right angles to the gill and 

 bear the spores. At how many points (sterigmata) on each basidium 

 are spores attached ? Draw a basidium, preferably one from which 

 the spores have not yet fallen. 



THE STUDY OF YEAST (SACCHAROMYCES CEREVISI^) 



320. Growth of Yeast in Dilute Syrup. — Mix about an eighth of 

 a cake of compressed yeast with about a teaspoonful of water and 

 stir until a smooth, thin mixture is formed. Add this to about half 



a pint of water in which a table- 

 spoonful of molasses has been 

 dissolved. Place this mixture in 

 a wide-mouthed bottle which holds 

 one or one and a half pints, stop- 

 per very loosely ^ and set aside for 

 from twelve to twenty-four hours 

 in a place in which the temper- 

 ature will be from 70 to 90 degrees. 

 Watch the liquid meantime and 

 note : 



(a) The rise of bubbles of gas 

 in the liquid. 



(6) The increasing muddiness 

 of the liquid, a considerable sedi- 

 ment usually collecting at the end 

 of the time mentioned. 



(c) The effect of cooling off the 

 contents of the bottle by immers- 

 ing it in broken ice if convenient, 

 or, if this is not practicable, by 

 standing it for half an hour in a pail of the coldest water obtainable, 

 or leaving it for an hoitt in a refrigerator, afterwards warming the 

 liquid again. 



(d) The effect of shutting out light from the contents of the 

 bottle by covering it with a tight box or large tin can. 



1 If the cork is crowded into the neck with any considerable force, pressure 

 of gas and an explosion may result. 



Fig . 196. — Part of the Preceding Figure. 

 (X about 300.) 



C, layer of cells immediately under the 

 hymenium ; s, a', s", three succesBive 

 stages in growth of spores. 



