284 



Diseases of Economic Plants 



as early as 1760. The disease may attack any part of the 

 plant at any age, — leaves, stalks, aerial roots, ears, tas- 

 sels, — provided only that they be still in tender growing 

 condition, not mature and hard. 



The first s>nnptom 

 is a pale, glistening, 

 swollen area covered 

 with a white mem- 

 brane, which soon ap- 

 pears black owing to 

 matured spores 

 within. The mem- 

 I3 r a n e eventually 

 bursts, loosening a 

 powdery, dry, black 

 m ass of spores 

 through which fibrous 

 veins of the corn 

 plant still penetrate. 

 It has ])een conclu- 

 sively demonstrated 

 that the causal fungus 

 is not conveyed to 

 the new crop in the 

 seed, as is the case 

 with so many other 

 smuts, and that there- 

 fore no form of seed 

 treatment is of value 

 for its prevention. 



It has been clearly 

 shown that infection 

 is produced by the 

 spores which, under 

 suitable conditions of moisture, fall upon any tender part of 

 the corn plant. The silks furnish the requisite conditions, 

 and it is through them that ear infection occurs. The 



Fig. 148. — Corn smut upon the ear. 

 Original. 



