FIELD DISEASES 147 



Natural or artificial infection can only 

 take place on mature plants which have 

 started to bloom. All attempts to inocu- 

 late plants in all stages of growth previous 

 to the blooming period have failed. It 

 seems that the host previous to blooming 

 possesses certain protective properties 

 which inhibit the growth of the parasite. 

 The disease in the field does not make its 

 appearance until the plants have started 

 to bloom. 



Over 1,500 plate cultures of incipient or 

 young lesions were made from the sweet 

 pea and clover. The organism may almost 

 invariably be taken in pure cultures from 

 the young lesions in the stems of sweet 

 peas when the surface is properly steril- 

 ized. The parasite is a yellow organism 

 which will grow luxuriantly upon any 

 nutrient media containing sugars. On 

 standard nutrient glucose agar the colonies 



