230 ELEMENTS OF BOTANY 
THE STUDY OF YEAST 
(SACCHAROMYCES CEREVISLE) 
296. Growth of Yeast in Dilute Syrup. — Mix about an eighth of 
a cake of compressed yeast with about a teaspoouful of water and 
stir until a sinooth, thin mixture is formed. Add this to about half 
a pint of water in which a table- 
spoonful of molasses has been dis- 
solved. Place this mixture in a 
wide-mouthed bottle which holds 
one or one and a half pints, stopper 
very loosely, and set aside for from 
twelve to twenty-four hours in a 
place in which the temperature will 
be from 70 to 90 degrees. Watch 
the liquid meantime and note: 
(a) The rise of bubbles of gas in 
the lquid. 
(b) The increasing muddiness of 
the liquid, a considerable sediment 
usually collecting at the end of the 
time mentioned. 
(c) The effect of cooling off the 
Fic. 165. Part of the Preceding contents of the bottle by immersing 
Figure. (x about 300.) it in broken ice if convenient, or, if 
C, layer of cells immediately under this is not practicable, by standing 
the-byMenaum s,s’,s, three suc: i+ for half an hour in a pail of the 
cessive stages in growth of spores. ; ‘ 
coldest water obtainable, or leaving 
it for an hour ina refrigerator, afterwards warming the hquid again. 
(7) The effect of shutting out light from the contents of the bottle 
by covering it with a tight box or large tin can. 
(e) The result of filling a test-tube or a very small bottle with 
some of the syrup-and-yeast mixture, from which gas-bubbles are 
freely rising, and immersing the small bottle up to the top of the 
neck for fifteen minutes in boiling water. Allow this bottle to 
1 Tf the cork is crowded into the neck with any considerable force, pressure 
of gas and an explosion may result. 
