THE MONTHLY BULLETIN. 



45 



as that to which the patient is susceptible. This treatment by immuni- 

 zation is still in the experimental stage and much investigation of hay 

 fever plants and of methods of treatment will be necessary before it 

 can be universally employed. 



The study of the causes of hay fever in this country lias been carried 

 on largely by the American Ilay-Fever-Prevention Association. The 

 work has consisted of a determination of the weeds that cause the disease, 

 the education of the public to the injurious effects of these plants, and 



Fig. 8. Greater Ragweed. Ambrosia trifida, a southern 

 species which is a chief cause of hay fever. Another 

 species of this plant, Ambrosia psilostachya, is found 

 in California. (After Clark and Fletcher.) 



an attempt at their suppression through cooperation and legislation, 

 ll lias been shown that in some districts, notably in New Orleans, the 

 number of hay fever eases has been greatly reduced through the weed- 

 cutting campaigns fostered by this organization and supported in some 

 eases by local ordinances. 



In California the study has only begun. Through cooperation with 

 the botanical department of the State University and with local botan- 

 ists and physicians the association just mentioned has been assembling 

 i lata and making tests of all plant species under suspicion, so far as 

 pollen could be obtained. Dr. Grant Selfridge, a San Francisco special- 

 ist, has inaugurated a botanical survey of certain districts in order to 



