THE CLOVER RUST 



221 



ium stage. It affects both the leaves and stems, produc- 

 ing cup-like swellings, which are filled with orange 

 colored spores. A white clover leaf attacked by this 

 stage of the fungus is shown in Fig. 89 a, while at c, 

 Fig. 90, may be seen two of the cluster-cujDs magnified, 

 and some of the orange colored spores still more enlarged. 

 These orange spores are blown to other clover plants, 

 especially red clover, where they germinate and send 

 their little tubes into the leaf tissues. These tubes start 

 the mycelium which develops between the leaf cells for 

 some time before any external indication of its presence 

 occurs. Then it produces, at certain places just beneath 

 the outer skin of the leaflets, numbers of small reddish- 

 brown spores, wdiich finally rupture the skin (as seen in 

 Fig. 90 /), and are set free. When magnified {d) these 

 spores are shovi^n to have their outer surfaces studded 

 with minute j^ointed tubercles. This is the second, or 

 uredo stage of the fungus ; these spores are called uredo- 

 spores. After these are mostly blown away — presumably 

 to start the disease in new situations — there is produced 

 from the same mycelium, and in the same spots, the third 

 form of spores called the teleuto-spores {e). These are 

 supposed to carry the fungus through the winter, although 

 it is probable that ir also passes the winter in the myce- 

 lium in white clover plants. 



Treatment. — According to Miss J. K Howell, of 

 the Cornell University, to whom we are indebted for 

 much of our knowledge of this disease, the early crop of 

 red clover is not likely to be injured by rust. In conse- 

 quence, she makes the following suggestions as to rem- 

 edies : ^^As the second crop is likely to suffer greatly if 

 the midsummer is cool, and as clover becomes a valuable 

 fertilizer when plowed in, the fields should be carefuUv 

 watched in such seasons, and the crop might be plowed 

 under to advantage. Burning the clover fields in the 

 fall would probably have some effect in checking the 



