J*>^ PEl'PKlt TKKK AS A CAUSE OF HAY FEVER. 



the dominant shrub on the hills to the north of the town. In 

 cutaneous tests on three tj^pical epidemic patients its pollen pro- 

 duced no reaction, whereas a control test made with pepper tree 

 I)ollen gave a strong reaction in all three patients. 



8_ Arfeniisia afra Jacq. — This is the plant locally' known 

 as the Wormwood or Wilde Als. Except for single grains, which 

 occurred on four plates, this pollen was found only once, but its 

 presence is of great importance because of its extreme virulence. 

 This was demonstrated by Dr. Scheppegrell (1917), who, in tests 

 covering a large variety of American hay-fever pollens, found 

 that of Artemisia considerably the most virulent. Artemisia is 

 one of the commonest hay-fever plants in the dry inland regions 

 of the United States, where several species are common, one, 

 the Sagebrush, forming the principal vegetation over thousands 

 of acres. Near Bloemfontein Artemisia is found to-day in only 

 small quantities, single plants and small patches occurring on the 

 hills to the north and nortli-east of the town. The amount of the 

 l)lant in the vicinity of the town is insufficient to suggest that it 

 could be a general cause of hay-fever, and the small amount of 

 its pollen fovmd on the plates is probably in fair proportion to its 

 importance in this connection. 



4. The only other pollen found more than once on the plates 

 was an undetermined grass which was present on three occasions. 



5. It will be noticed that, except for pepper tree pollen, the 

 total amount of pollen in the air of the town is small and th,e 

 number of kinds few. This is the case at all the centres at which 

 plates were exposed, but most noticeably so at the Ramblers' 

 Club. During the epidemic seasons of 1919, 1920 and 1921, plates 

 were exposed here over a total period of 57 days and yet, except 

 for single grains, pollen other than that of the pepper tree was 

 found on onlj' 2 plates, on one of which the only pollen, in 

 addition to that of the pepper tree, was that of a cultivated pine. 

 Yet at this site the plates were hung some 28 feet above the 

 ground on a balconj- with free exposure to the wind, where they 

 might be expected to catch any pollens floating in the air. 



The great variation in the pollen found on plafes exposed at 

 the same time and for the same period in different parts of the 

 town is one of the noteworthy features shown in the Tables. 

 The distribution of the pollens would indicate that they are 

 local in origin, since, if pollen had been carried for any consider- 

 able distance by the wind, it would have been more widely dis- 

 tributed. From the result shown in the Tables it would ap'^ear 

 that no pollen, not even that of the pepper tree, was distributed 

 through the air of the whole town. 



(b) Experiments m November and December, 1920. 



At Bloemfontein during the epidemic season of 1920. plates 

 were exposed on 10 days between November 25 and December 

 23. Particulars are given in Table VIII. The total mnnber of 

 plates exposed was 22, and the period of exposure varied from 

 24 to 72 hours. Dust was found on all the plates, often in large 

 quantities, and pepper tree pollen, in van'ing amounts, on 20 of 



