110 CLASSIFICATION OF THE MICRO-ORGANISMS. 



hyph multiply, become segmented, and break up into 

 spores, which then occupy the place of the tissue destroyed, 

 in the form of dark, dust-like masses. The short 

 germinating tube (promycelium) branches in single 

 segments (sporidia), which become detached from the 

 promycelium, and can again grow in the form of germina- 

 ting tubes. Different species of these fungi attack different 



parts of the plant, 

 n now the flower, 



now the stalk and 



of 



Fig. 1. Ustilago carbo X 400. 



A, ripe spores. 



, forming promycelium 



flower, and now 

 the root. The 

 detection of the 

 disease depends 

 chiefly on the 

 presence of the 

 dark masses of 



spores. Continued moisture is necessary for the germi- 

 nation of the spores, and for the penetration of the 

 germinating tubes into the host. The disease is pre- 

 vented by diminution 

 of the moisture, or by 

 disinfection of the 

 grain, e.g., by means 

 of sulphate of copper. 



Ustilago carbo (brand, 

 smut). A black powder 

 on the ears and panicles 

 of wheat, barley, and oats. 

 Atthetime of harvest the 

 brand mass,whichrapidly 

 breaks up, is removed by 

 wind and rain, and hence 

 there is no contamina- 

 tion of the meal. Spores 

 brown, spherical (fig. 1); 

 cpisporium smooth; 

 sporidia composed of 

 longish cells (fig. 1, B). 

 About 30 varieties. 



Tilletia, caries (smut). 

 A blackish brown 

 powder in the grains of 



Fig. 2. Tilletia caries X 400. 



sp, ripe spores. 



PPi sprouting spores, at a commenc- 

 ing development of the sporidia ; 

 at s fully formed sporidia united 

 in pairs. 



x, germinating tube of a sporidium. 



s 1 , secondary sporidia. 



