78 



little, perhaps, by plantain. Toward the end of July this type 

 of hayfever gradually dies out as the common grasses begin to 

 set their seed. Patients may even have comparative freedom 

 from symptoms for two or three weeks, or until the middle of 

 August when the third and worst hayfever season begins. This 

 is of the type which is called "ragweed fever," and with justi- 

 fication because it is almost entirely due to the pollen of the 

 ragweeds and their closest relatives. It goes on until all such 

 weeds, dry up, as they often do toward the end of summer, or 

 their flowering is stopped by an early frost. 



These three seasons differ greatly in their relative impor- 

 tance. Early-spring hayfever is comparatively unimportant in 

 the eastern part of the country, unimportant only because there 

 are few cases, not because such are milder for they may be very 

 severe. Among the earliest trees to flower in our region are the 

 elms. Generally the first elm pollen may be detected in the air 

 about the first of April, and very soon thereafter the elm-hay- 

 fever patients begin to have their troubles. Farther south where 

 spring comes earlier the tree hayfever season also begins earlier. 

 I once knew of an elm-hayfever patient who came north just 

 ahead of the flowering of the southern elms, then returned south 

 just ahead of the flowering of the northern elms. It was con- 

 sidered a very satisfactory way to spend a short vacation. 



There are several other trees belonging to this very early 

 period but of considerably less importance. Of these the willows 

 begin to flower at about the same time as the elms, but they do 

 not shed nearly so much pollen consequently they claim fewer 

 victims and these are less affected, but their troubles may be 

 greatly prolonged because there are so many kinds of willow 

 flowering at different times that as soon as one kind has finished 

 another takes its place. The season starts with the pussy willows 

 as, for example, Salix discolor and 5. purpurea flowering very 

 early, generally in March much before the opening of the leaves. 

 It is continued with the tree willows such as the crackle willow 

 (5. fragilis) and the black willow {S. nigra) which flower either 

 at the same time or just after the leaves unfold, continuing the 

 season to nearly the end of May. Also belonging to the early 

 season are the poplars. Though they shed excessive amounts of 

 pollen, cases of hayfever from it are rare in the eastern states 

 and generally of a mild character. The same is true of the 



