32 



dry they are easily blown about by the wind and so become 

 scattered over a large field. Many of them are covered with 

 minute projections which enable them to adhere to the surface 

 of plants and various other substances, and are thus carried 

 about as sandburs or cockle-burs are- 



THE KUSTS (Uredineae}. 



The rusts are without doubt the most injurious of all fungi. 

 They are also the most difficult to destroy or prevent. This is 

 doubtless due to their natural facilities for insuring reproduc- 

 tion. Normally a rust, as for example the common wheat rust 

 Puccinia graminis), passes through three readily recognized 

 stages of growth on the same host plant or on different hosts as 

 the case may be. Stage I, known as the "Cluster Cap" stage 

 consists of numerous small orange colored cup shaped bodies, 

 arranged in clusters or scattered uniformly upon the surface of 

 the host. These "cups" are filled with yellowish spores which 

 fall upon the surface of the host plant, germinate, and give rise 

 to staye II, or the "Red Rust" stage. This may be readily re- 

 cognized in the reddish powdery masses covering the various 

 small grains just before harvest on a bad "rust" season. Tho 

 spores of this stage are born in small redish or blackish, often 

 elongated, openings in the epidermis of the host. These are 

 called sori (singular sorus). The red rust spores fall upon the 

 host and germinate very readily producing stage III, or the 

 "Black Rust" stage. Sometimes however the same sori that pro- 

 duced red rust spores produce black rust spores later in the 

 season. Black rust is by far the most destructive of all the stages 

 of these fungi. The black rust spores constitute the resting 

 spores. They lie in the straw or upon the ground till spring 

 when they germinate and produce minute colorless bodies which 

 attach themselves to the young host plant, germinates, and the 

 fungus starts on its round of life once more. 



REMEDIES AND PREVENTIVES OF FUNGOUS DISEASES. 



To combat fungous diseases successfully the greater part of 

 the work should be done in endeavoring to prevent the disease 

 rather than to try to cure it after it has gotten a start. While 



