FUNGI 81 
rust upon wheat and oats; the smut that forms the black 
powdery or sticky masses upon corn; the cedar-apples, 
which are fungous growths forming peculiar hard or gelat- 
inous balls on branches of various evergreen trees; puff- 
balls and toadstools of various kinds. Place some ordinary 
yeast in some water to which a little sugar has been added. 
For a study of bacteria obtain some water containing decay- 
ing organic matter, and put two or three dishes of it in a 
warm place, where the bacteria will reproduce rapidly. 
Note the general form of these various Fungi and try to 
determine how they live and how they affect the things that 
furnish them nourishment. A good notion of the yeasts 
and bacteria can be had only by means of strong magnifica- 
tion. The last two groups of Fungi mentioned are very 
simple in structure, but their economic importance is very 
great. Why? 
Sketches should be made of the different kinds of Fungi 
observed in this exercise. 
LESSON XLV 
A lichen 
If Part I of the manual is not to be used, introduce here 
the exercise on the lichen in Lesson XXIII. 
