Minnesota Plant Diseases. 



393 



rounded by a protective coat of smaller, lighter spores, which 

 have lost their power of germination. The spore balls escape 

 intact as the smut powder. 



Carnation smut [Ustilago molacea (P.) Fckl.]. This smut 

 is often found on wild plants of the pink family; e. g., on chick- 

 weeds, starworts, catch-flies, soapworts and corn cockles. See 

 Diseases of Greenhouse and Ornamental Plants. 



FIG. 209. Mint rust. Winter spore clusters on the leaves. Original. 



Smut of violet [Urocystis violae (Sow.) Fisch.]. One oc- 

 casionally meets with this smut on wild violets. It may occur 

 on leaf-blades, petioles, stems or flower stalks. Definite pus- 

 tules are formed which, when broken, disclose a black, powdery 

 spore-mass. The flowers do not seem to be attacked and the 

 anthers are not smutted, as in the carnation smut. The smut 

 spores are formed in ball-like masses of cells, the outer of which 



