112 USTILAGO MAIDIS. 



covered with openings or blotches, where the spores have broken 

 through, and the outside very much darkened by their presence. 

 Almost every one is so well acquainted with the appearance and 

 growth of this smut that it is not necessary to enter at any length 

 into the details. 



Fig. 2 represents one of the bracts alone, with a cross section of 

 the same, showing how the internal structure of the bract is changed 

 from its normal appearance, and is packed full of the fine spore 

 dust. 



In fig. 3 we have the spores of the Ustilago Maidis ; they are 

 almost as light as the air, and can be carried for a great distance by 

 the wind, the whole outer surface of the spore is covered with 

 minute spines or thorns*; they are of a dark-brown color, nearly 

 opaque, and have a singularly pungent and offensive odor. The 

 protoplasm of the spores is contained within a central cell or sack ; 



- 3- 9 Diameters. 



each spore has two surrounding membranes, the inner thin and 

 nearly transparent, while the outer is dark-brown and roughened. 

 At b we see a filament or little root just developing from one of the 

 spores. This delicate root works its way into the tissue of the stem, 

 leaf or some part of the corn, and continues to grow until a perfect 

 net-work of roots is made ; then after some intermediate steps there 

 develops the great mass of spores which constitute the so-called 

 corn ergot. On account of their extremely thick walls, it is hard to 

 check or destroy this disease. 



When Ustilago Maidis appears in its natural condition in com- 

 merce, it is a mixture of almost everything pertaining to blighted 

 corn, corn smut, powdered corn leaves, etc., even frequently con- 

 taining the powdered cob. When the greater part of the coarse 



