257 



stroys so much of the leaf surface, and appropriates so 

 much of the nutriment of the plant, that the grain is light 

 .and poor in quality, and often greatly deficient in quantity. 

 A little later in the season a second kind of spore is de- 

 veloped on the rust mycelium. These form short black 

 lines on the leaves and stems. They are called winter 

 spores, because their office is to carry the fungus through 

 the winter. They are long and narrow, and are divided by 

 a cross partition into two cells. They are darker colored, 

 and the cell wall is thicker than in the red or summer spores. 

 This fungus is a good example of the true rusts ( Uredineae). 

 They form a large group and include some of our most 

 troublesome diseases. As a rule they do not yield readily 

 to treatment. No practical remedy has been found for the 

 oat rust. Some varieties of oats, however, suffer less from 

 the disease than others. In this State it is usually only the 

 resistant or so called "rust proof" varieties that are planted. 

 Something moreover can be done by methods of planting 

 and fertilizing, to help the oat plant to resist the rust. On 

 some soils oats will rust less when plowed in, thus cover- 

 ing the seed more deeply, and producing a deeper rooting 

 habit than when merely brushed and harrowed in after the 

 land is plowed. Excessive applications of nitrogenous fer- 

 tilizers like stable manure or cottonseed meal that cause a 

 soft, succulent growth, are more apt to favor rust than 

 where the mineral elements, phosphates and potash, pre- 

 dominate in the fertilizer, and the growth is harder and 

 less rapid. 



Other serious diseases of oats occur, but they will not be 

 considered here. 



COTTON. 



The diseases of cotton have been studied by the officers 

 of this station, and have been discussed in Bulletins 21, 27, 

 36,41 and 55. In Bulletin 41, Professor Atkinson described 

 all the cotton diseases that had been observed by him, and 

 the reader is referred to that bulletin for a detailed dis- 



