LIFE HISTORIES OF FUNGI 
269 
261. Reproduction by Asci. In late summer or early 
fall one may notice, on an infected leaf, among the my- 
celium, tiny black dots or spheres (Fig. 194), whence the 
name, Microsphcera. Examined with the microscope, these 
bodies are seen to bear numerous appendages, branched 
at the end, and with the tips of the branches curved back to 
form miniature hooks (Fig. 195). When these little spheres 
are crushed, or when they burst open, they are found to con- 
FIG. 194. Powdery mildew (Micros phccr a Alni} on lilac leaf. An in- 
fected area from the leaf in Fig. 193, greatly magnified. 
tain a number of tiny sacs or asci (singular ascus}, whence 
the name "sac-fungus," or Ascomycete. In each ascus are 
a number of spores or ascospores, formed from the con- 
tents of the ascus. The young ascus is, therefore, a spore- 
mother-cell. There are usually eight ascospores in an 
ascus, but the number may vary. 
The spherical case containing the asci is the "spore- 
fruit" (ascocarp or peril hecium), and results from the 
fusion of the contents of an antheridium and an oogonium 
