44 THE MONTHLY BULLETIN. 



THE RELATION OF FARM WEEDS TO HAY FEVER. 

 By Habvet Monroe Hall. 



That plants have for a long time been considered as in some manner 

 connected with the cause of hay fever is indicated by the name of this 

 malady. It was not until recent years, however, that the exact relation 

 of plant pollen to the disease was scientifically established. Today it is 

 well known that pollen produced by the flowers of certain plants 

 is directly responsible for most cases of hay fever. Since something 

 over one million sufferers in the United States are personally interested 

 in the suppression of the plants which cause their trouble, and since 

 at least a portion of these plants are also objectionable as agricultural 

 weeds, it may be worth while for those interested in weed legislation 

 to keep in touch with the work of physicians and others aiming at the 

 prevention of hay fever. 



There has been much misconception in the public mind as to the kinds 

 of plants that cause the disease. Many sufferers, and even physicians, 

 have supposed that it was caused by plants with conspicuous and showy 

 flowers. This, however, is seldom the ease. The reason is obvious. 

 The pollen produced by large or showy blossoms is almost always insect 

 carried, is therefore relatively heavy and not produced in great abun- 

 dance. On the other hand, most plants with small, inconspicuous flowers, 

 are wind pollinated, their pollen is therefore light and produced in 

 great abundance, and it is this voluminous, light-weight pollen that 

 reaches the nostrils of susceptible people and causes the trouble. The 

 patient, untieing the showy flowers of a neighbor's orchard trees or 

 ornamental shrubbery, is likely to hold these responsible for his hay 

 fever, whereas the cause is much more likely to be the homely, neglected 

 weeds of the roadside or of his own back yard, the blooming period 

 of these overlooked weeds being the same as that of the flowers to which 

 he has assigned the blame. 



It is thus seen that in any attempt to determine which plants arc 

 the cause of hay fever in a particular district, the wind pollinated ones 

 should be examined first. But not all such arc causative factors and, 

 on the other hand, it is possible that a few insect pollinated species 

 may sometimes produce the disease, at least when large quantities of 

 the flowers are brought near to a susceptible person. Often the botan- 

 ical relationship of a plant will furnish a clue as to whether or not a 

 suspected species is injurious. Thus, when it was found by experiment 

 that ragweed was actually a source of hay fever, other members of the 

 ragweed tribe of composites, such as poverty weed, cocklebur, Franseria, 

 etc.. were examined, and all thus far tested have given positive results. 



The final criterion in all cases is what is known as the "biological 

 lest." This consists of applying a small amount of the pollen to the 

 nostril of a person susceptible to hay fever, or to the angle of the eye. 

 Tf the well known hay fever symptoms develop, the plant from which 

 the pollen was taken is then classed as a hay fever species. Skin 

 reactions are also induced with solutions of the pollens, and in this 

 manner the exact species which has caused hay fever in a patimit may 

 sometimes be determined by the clever physician. Even a resistance 

 to the disease is sometimes built up by injecting from time to time 

 small amounts of a vaccine prepared from the same kind of pollen 



