298 Journal of Agricultural Research voi.xx,n . 4 



to observe the disease extensively, concludes that crownwart decreases 

 the yield and shortens the life period of plants. He says: 



Alfalfa fields that had the crown wart in abundance in 19 14 produced good crops of 

 hay in that year and in 1915. In one field sown in 1910 that has been under obser- 

 vation the past two years, practically every plant has galls. This field has produced 

 apparently normal crops of hay, but more critical observation shows decreased vigor 

 in the plants and a corresponding decrease of yield. 



McKee believes the disease much more widespread than is commonly 

 supposed and urges work to determine its importance in alfalfa culture. 



Thus it appears that although the disease is scattered through large 

 alfalfa-growing areas in the United States, yet it does not appear at any 

 place to have become regarded as a serious limiting factor in the growth 

 of the crop, except during years of severe attack and even then in small 

 areas. 



The writers have not attempted to determine the present limits of 

 spread of the disease in the United States. A limited amount of time has 

 been spent in the spring of three years observing the disease, chiefly in 

 the river valleys where it is known to be most abundant, the Sacramento 

 River Valley in California and the Rogue River Valley in Oregon. The 

 second of these years, 19 18, appears to have been distinctly unfavorable 

 for the development of the disease, especially in California. The winter 

 rainfall was below normal, in consequence of which the Sacrafnento 

 River did not overflow its flood plain where McKee observed the disease 

 to be most abundant. The disease was commonly present on a larger or 

 smaller percentage of plants, but nowhere did observation bring con- 

 viction that considerable damage was being done. In the San Joaquin 

 Valley that year only occasional diseased plants could be found, though 

 in some localities there was excellent testimony from farmers of the 

 abundance of the disease in previous years. 



In 19 1 9 there was much more winter rain, especially in the Sacra- 

 mento River Valley, and a greater amount of disease was found. Even 

 then it was only rarely that the disease was sufficiently abundant to appear 

 to be of serious economic importance. Plants could be found whose 

 early buds had become so completely infected that few were left to form 

 the second and later cuttings, but such plants were usually widely scat- 

 tered among others less severely infected. Rarely indeed does the dis- 

 ease appear to be solely responsible for the killing of entire plants, though 

 it must often weaken them. A significant estimate of the actual damage 

 done can be made only after careful observation has extended over a 

 period of years when the varying intensity of the annual attacks can be 

 studied and the behavior of the diseased plants followed throughout the 

 year. 



DESCRIPTION OF THE DISEASE (PL. 47) 



The disease is more easily described by stating briefly the origin and 

 method of development of the galls. So far as the writers can discover 



