426 VIOLET ROOT-FUNGUS. GRASS MILDEW. 



Red clover is, also, often marked in the summer and fall by" 

 similar but darker brown spots, bearing in the center of each a 

 brown cup, scarcely. 1.32 in. in diameter, that opens irregularly 

 at the top and so allows the escape of its spores. This is Phacid- 

 ium (or Pseudopeziza) trifolii, which at times does considerable 

 damage in Europe. (Consult Fig. 171.) 



9. The violet root-fungus (Leptosplmria circinans, Fcke.) 

 Forming a violet mold on the roots of alfalfa, red clover, etc., 

 which soon rot, the parts above ground turning yellow and 

 dying. . 



In Europe, Lucerne is subject to a disease that manifests itself 

 by the appearance of yellow spots in the fields. These spread 

 until the entire crop is often affected. The trouble lies in a. 

 violet-colored mold that develops on the roots of the plants, 

 spreading from one to another through the soil, and finally pro- 

 ducing spores by which it is apparently carried over the winter. 

 This disease has not been recognized yet in the United States,, 

 but what is held to be a state of the root fungus a cobwebby,, 

 white mycelium, known as the snow-mold, that covers the- 

 ground, leaves, etc. , just as the snow disappears in early spring 

 has been noticed in great abundance at River Falls, Wis., by 

 my friend, Professor King, so that it is not improbable that the 

 parasitic form will soon be found. No remedies for it have been 

 proposed, except digging ditches, as deep as the roots extend, 

 about diseased parts of the field when it first appears to prevent 

 it from spreading. 



10. The grass-mildew, (Erysiphe graminis, D. C.) Forming- 

 a pure white, cobwebby or mealy coating on the upper side of 

 the leaves of grasses, especially in the shade 



The German equivalent (meal-dew) of our common name for 

 the group of fungi to which this species belongs is expressive of 

 the appearance presented by them in their early stages. When 

 they cover the surface of the plants they grow on with a fine* 



