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similar toxicity and sometimes adds a little to the troubles of 

 the hayfever sufferer. Still, in spite of these additions, the load 

 of toxic pollen in the air gradually tapers off, but does not 

 actually reach zero until well into October, unless halted by an 

 early frost. 



In California and the southwestern states there is the western 

 ragweed (Ambrosia psilostachya) similar in appearance to the 

 eastern short ragweed. In the South, eastern Texas, and the 

 lower Mississippi valley, is the western giant ragweed {A. 

 aptera), and in the mid-western prairie states, Louisiana and 

 eastern Texas, is the southern ragweed (A. hidentata). In Florida 

 there is the coast ragweed {A. hispida) which, however, appears 

 to be a negligible factor in hayfever. It is safe to say that not 

 a state in the Union is entirely free of ragweeds. Besides this 

 the ragweeds have a number of very close relatives which are 

 essentially the same in their effects on hayfever patients. There 

 is the genus called the false ragweeds (Franseria) so close to 

 the true ragweeds in appearance that it is difficult to tell them 

 apart. Two of these are counted as very bad hayfever plants; 

 the bur ragweed {F. acanthocarpa) is a common weed almost 

 throughout the Rocky Mountain states and westward to the 

 coast range, and the slender ragweed [F. tenuifolia) is character- 

 istic of the arid plains of our southwestern states from Kansas 

 and Oklahoma to southern California. Still another genus, not 

 quite so closely related to the ragweeds yet close enough to be 

 nearly the same thing as far as the hayfever patient is con- 

 cerned, is the genus of marsh elders (Iva). In the east we have a 

 marsh elder common in tidal marshes along the Atlantic coast. 

 In the Torrey Club area it is known as Iva oraria. It extends 

 from Massachussets southward along the Atlantic coast. Some- 

 where in Virginia its name is changed and from there it extends 

 on as Iva frutescens around Florida and along the Gulf coast. 

 It causes little trouble to hayfever sufferers, none outside of the 

 immediate vicinity of the tidal marshes, but its pollen reacts 

 almost as violently as that of ragweed. The rough marsh elder 

 is a real hayfever plant of our midwestern prairie states from 

 Iowa and Nebraska southward, and the poverty weed (/. 

 axillaris) is often a factor of importance throughout much of 

 the huge region from southern Manitoba to Oklahoma and 

 westward almost to the Pacific coast. Still another member of 



