THE FUNGI 



277 



the puffball. Finally all of the tissues of the original kernel 

 are absorbed and the hyphse die, leaving the spores surrounded 

 by a thin hyphal membrane. The rupture of this membrane 



allows the spores to escape and to be 

 widely disseminated in the fields. 

 Like the black spores of the wheat 

 rust these smut spores carry the plant 

 over the winter and germinate in the 

 spring, producing the smaller spores, 

 or sporidia, which are blown to young 

 corn plants and start the fungus for 

 another season. 



Other smuts 

 on onions, wheat, 

 oats, etc. have a 

 history similar to 

 that of the corn 

 smut. The smuts 

 are very destruc- 

 tive where they 

 occur in abun- 

 dance, since they 

 attack the ker- 

 nels of the grains 

 affected and thus 

 cause the com- 

 plete destruction 

 of the seed. 



FIG. 154. Kernels of corn 



infected with corn smut 



(Ustilago zeae) 



Observe the outline of the ker- 

 nels still visible in the upper, 

 greatly swollen mass. After 

 Duggar 



FIG. 155. Spore germi- 

 nation in the spores of 

 corn smut ( Ustilago zeae) 



Note the conidia, or dis- 

 seminating and infecting 

 spores, being produced 

 from the sides of the sin- 

 gle germ tube, or hypha, 

 springing from the spore. 

 After Brefeld 



LICHENS 



Structure and habit. Lichens occur on the bark of trees, on 

 old fences, and even on earth and stones in certain localities. 

 They are grayish green in color and may occur as flat, leaflike 

 expansions (foliaceous lichens) (Fig. 156), as powdery crusts 

 (crustaceous lichens), or as shrubby, erect outgrowths (fruticose 

 lichens). The fruticose lichens often form conspicuous coverings 



