THE OKION SMUT 



153 



signs of smnt in its subsequent growth ; but, as a rule, 

 the same dark appearance shows itself in the second leaf 

 and those subsequently formed, and if the seedling is 

 pulled up and examined, the w^hole 

 plant will be found to be pervaded 

 by the disease, to a greater or less 

 extent. Plants thus diseased, espe- 

 cially if the soil is dry, very com- 

 monly succumb early, dying while 

 in the second or third leaf. The 

 stronger plants, however, especially 

 if the ground is moist, are able to 

 resist the smut sufficiently to make 

 a considerable growth, and many 

 survive even up to the time of har- 

 vesting. Fig. 67 represents such an 

 onion reduced to one-third its nat- 

 ural size, and is a typical example 

 of the appearance presented by smut- 

 ted onions that have survived until 

 midsummer. In such specimens the 

 smut shows itself by black eleva- 

 tions upon the bulb, running down 

 to its very base, and extending up 

 w^ard into the leaves, the outer of 

 which, in the present instance, have 

 split open, showing the characteristic 

 sooty powder composed of spores 

 mingled with the stringy mass of 

 dead leaf tissue. As a rule such 



1 T -ii 1 • FIG. 67. OKIOK AFFECTEI> 



onions always die, either drying up ^^ ^^^^^ one-thikd 

 or rotting soon after they are natural size. 

 pulled." When onions are grown upon the same land 

 for several successive seasons the smut, after it once gets 

 started, gradually increases, until, at the end of five or 

 more years, the soil is so full of smut that the field gen- 



