250 DISEASES OF FIELD & GARDEN CROPS. [CH. 



Brefeld ; in other cases three secondary spores may become 

 conjoined, and it is not uncommon to see the conjugating 

 band itself burst and produce a mycelial thread. 



Under favourable conditions a few germinating second- 

 ary spores will form a dense involved mass of mycelium, 

 bearing a vast number of conidia of the first and second 

 generation ; and under the microscope these may be seen 

 in all stages of growth. When the mycelium for any 

 reason ceases to grow, a crop of conidia is at once pro- 

 duced. Sometimes the mycelial threads become furnished 

 with an enormous number of short joints or constrictions, 

 giving the threads a necklace-like appearance. Ultimately 

 this chain or necklace breaks up into separate joints, and 

 each joint acts as a conidium. Each conidium thus 

 formed in a chain is capable of producing other necklace- 

 like growths of conidia. 



An elaborate essay on bunt and smut was published in 

 Paris in 1877 under the name of Aperfu SysUmatique des 

 Ustilaginfos, by Alexandre Fischer de Waldheim. This 

 author at one time advocated the idea of bunt and smut 

 fungi living in two forms on different plants in the sup- 

 posed style of corn mildew on the barberry bush, because 

 he failed to infect corn experimentally, and because he 

 had probably learned that " experience had taught the 

 practical farmer " that (according to Phillipar) the barberry 

 bush, a stinking plant, when in bloom, was in some places 

 the cause of bunt. No experiment is, however, easier 

 than the artificial and direct infection of wheat with bunt 

 and smut. 



Wheat becomes affected with bunt by the spores of the 

 fungus being sown with the grain. The spores do not 

 germinate whilst they are dry and stored with the seed, 

 but in and on the damp ground after the grain has been 

 planted. The whole series of changes illustrated in Fig. 

 116 takes place on and in the ground, and when the 

 attenuated thread at F is produced, it readily finds its 

 way, aided by its inconceivable fineness, into the tissues 



