80 A LABORATORY MANUAL OF BOTANY 
developed? Is it a waste of energy for plants to develop so 
many spores? What advantage is it to the puffballs to have 
some spores retained for a long time in the old plant? 
LESSON XLIII 
A mildew—lilac-mildew or smartweed-mildew 
General study.— Examine leaves of the plants on which 
the fungus is growing. Draw, showing the distribution of 
the mold-like mycelium and the small, dark, sphere-like 
bodies which contain the spores. 
Vegetative structure——Examine a section of the leaf, 
note the mycelium on the surface, and see how it enters 
the leaf. What are the functions of those branches of the 
hyphez that enter the leaf? 
Where is most of the fungus plant with reference to 
its host? 
Reproduction.—On the surface of the leaf will be seen 
small dark bodies, the closed cups, or cleistothecia, from the 
walls of which extend appendages with tips peculiar to each 
mildew. In these bodies are sacs, each of which contains 
spores. Orush open the “ fruiting bodies,” or cups, and 
study. How many sacs? How many spores in each sac? 
Draw. 
General suggestions.—The “ fruiting bodies ” are heavy 
walled and are suited to protect the spores through the win- 
ter season. How are spores set free in spring? Observe the 
lilacs, smartweeds, grape-vines, etc., to see how general is 
the distribution of these mildews. Of what economic im- 
portance are they? 
LESSON XLIV 
General exercise on Fungi 
Let each student bring into the laboratory as many 
kinds of Fungi as he can find. Look for specimens of the 
