100 DISEASES OF CBOPS. 



be steeped in a solution of copper sulphate or common 

 salt. 



The Smut Fungus {Ustilago carbo, Fig. 39) pro- 

 duces the well-known black and withered ears of corn. 

 It attacks barley, wheat, and certain grasses, as well as 

 oats. The disease is said to originate in the roots of the 

 host-plants, and passes up the stems into the leaves and 



Fig. 39. — The Smut op Coen [Ustilago carbo). 



A. Oats infested with Ustilago carbo (a). 



B. " Sori " on a portion of a glume of oats. 

 0. Spores x 330 (Zeiss' D., 3oo.). 



E & D. A spore germinating. 



panicles. The spikelets (Fig. 39 A) become covered with 

 masses (sori) of black or primary spores, which work their 

 way from within outwards, and ultimately rupture the 

 epidermis of infested plants. The small globular spores 

 are of a dark-brown colour, almost black (Fig. 39 C). 

 These spores give rise to " buds " (Fig. 39 E), which ulti- 

 mately form secondary spores, or conidia. The secondary 

 spores are produced by what is known as the process of 



