60 SOUTHERN FIELD CROPS 



dant and injurious wlien unfavorable conditions result in a 

 thin stand of wheat. There is no foundation for the behef 

 that wheat may turn to cheat. The cheat comes only from 

 cheat seeds, which are much smaller and lighter than wheat 

 grains. Hence, cheat seed can be separated from wheat 

 by the fanning machine, or by immersing the seed in water, 

 when the sound wheat grains sink, while the cheat seeds 

 float and may be skimmed off. 



Cockle is an annual plant with large pinlc flowers and 

 black seeds. The latter are so nearly of the same diameter 

 as grains of wheat that their separation is not easy, and 

 their retention results in very inferior flour. Avoid sowing 

 wheat with these black seed in it. If occasional plants of 

 cockle appear, they should be pulled. 



Wild garlic (wild onion) and -peiypergrass are among the 

 other weeds often found in wheat fields. The fanning and 

 screening of the seed wheat is the usual means of avoiding 

 peppergrass and other weeds. Recent experiments have 

 showir that millers can separate onion bulblets from wheat 

 by artificially drjdng the wheat and then passing it through 

 the ordinary cleaning machinery of the mills. (U. S. Dept. 

 Agr., Bur. Plant Ind., Bui. No. 100, Part III.) 



66. Diseases. — Ruds are the most injurious diseases 

 of wheat. The rusts are caused by certain microscopic 

 organisms (fungi) . Both the leaves and stems may be af- 

 fected and changed from a green color by a series of small 

 reddish or black spots from which may arise clouds of pow- 

 dery spores, or propagating bodies. The destruction of the 

 green coloring matter in the leaf prevents the formation of 

 starch, and results in poor yields of small, shriveled grains. 

 Dampness and heat, favor rust. Varieties ripening early 



