266 



FOUNDATIONS OF BOTANY 



C 



fruiting cells (basidia) which 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 CERE VISILE) 



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 1 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 hour 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. 



S' 



FIG. 196. Part of the Preceding Figure, 

 (x about 300.) 



(7, layer of cells immediately under the 

 hymenium ; s, s', s", three successive 

 stages in growth of spores. 



