FUNGI. 



65 



(Ustillago maydis). This familiar fungus attacks Indian corn, 

 forming its spores in enormous quantities in various parts of 

 the diseased plant, but particularly in the flowers ("tassel" 

 and young ear). 



The filaments, which resemble somewhat those of the white rusts, 

 penetrate all parts of the plant, and as the time approaches for the forma- 

 tion of the spores, these branch ex- 

 tensively, and at the same time be- 

 come soft and mucilaginous (Fig. 38, 

 Z2). The ends of these short branches 

 enlarge rapidly and become shut off 

 by partitions, and in each a globular 

 spore (Fig. 38, (7) is produced. The 

 outer wall is very dark-colored and 

 provided with short spines. To study 

 the filaments and spore formation, 

 very thin sections should be made 

 through the young kernels or other 

 parts in the vicinity, before they are 

 noticeably distorted by the growth of 

 the spore-bearing filaments. 







FIG. 38. A," tassel " of corn attacked 

 by smut (Ustillago). B, fila- 

 ments of the fungus from a thin 

 section of a diseased grain, show- 

 ing the beginning of the formation 

 of the spores, x 300. C, ripe 

 spores, x 300. 



As the spores are forming, an abnormal growth is set up in 

 the cells of the part attacked, which in consequence becomes 

 enormously enlarged (Fig. 38, A), single grains sometimes 

 growing as large as a walnut. As the spores ripen, the affected 

 parts, which are at first white, become a livid gray, due to the 

 black spores shining through the overlying white tissues. 

 Finally ^the masses of spores burst through the overlying 

 cells, appearing like masses of soot, whence the popular name 

 for the plant. 



The remaining Mycomycetes are pretty readily divisible into 

 two great classes, based upon the arrangement of the spores. 

 The first of these is known as the Ascomycetes (Sac fungi), the 

 other the Basidiomycetes (mushrooms, puff-balls, etc.). 



