194 PEPPER TUEE AS A CAUSE OF IIAY FEVER. 



Two senior students, Mr. C. J. C. Lemmer, and Mr. L. P. 

 Spies have helped considerably, especially during the summer 

 vacation of 1920-21, when there was a great pressure of work 

 owing to the arrival of pollen plates exposed at other centres. 



I am indebted to Mr. J. A. Caskie, City Engineer, Bloem- 

 fontein, for access to the evaporation records taken at Mazels- 

 poort; and to Mr. C. Stewart, Chief Meteorologist, for the weather 

 statistics, and especially for access to the Bloemfontein records. 



Thanks are due to friends and officials at Kimberley, 

 Grahamstown, Maritzburg, and Johannesburg, for exposing 

 pollen plates and supplying information regarding the number of 

 pepper trees. In this connection I should like especially to thank 

 Mr. J. Hewitt, Director of the Albany Museum, Grahamstown, 

 and Mr. Eeginald W. H. Wisbey, then Science Master at the 

 Kimberley Boys' High School. 



I am indebted to the Government Printing and Stationery 

 Office for the loan of the block to reproduce Figure 1 from Mr. 

 Cox's article in a recent memoir of the Botanical Survey. The 

 inoculation tests were again performed by Dr. S. M. de Koek ; 

 and the numerous tables have been prepared by Miss D. M. 

 Gemmell, Demonstrator in Botany. 



XIX. Summary. 



Bloemfontein and Ivimberley are subject to severe epidemics 

 of hay fever in the early summer, especially in November and 

 December. By the exposure of pollen plates, it was showai that 

 the pollen of the pepper tree is virtually the only kind of pollen 

 frequent in the air of Bloemfontein during the epidemics. Inocu- 

 lation tests showed that hay fever patients reacted to pepper tree 

 pollen; and this was the only kind of pollen found in the nasal 

 discharge of epidemic patients. It is, therefore, concluded that 

 the pepper tree is the cause of these epidemics, to which, indeed, 

 they are popularly attributed. An account is given of the climate 

 of Bloemfontein ; and it is pointed out, that the pollen of this tree, 

 which is normally sticky and carried by insects, becomes dry and 

 powdery and is dispersed by the wind in the hot, dry weather 

 prevalent in Bloemfontein during the epidemic season. Attention 

 is called to many other ways in which the dry climate of Bloem- 

 fontein affects the epidemics. The difficulties in accepting the 

 pepper tree as a cause of hay fever are dealt with. These are: 

 the large size of its pollen; pollination by insects; and that the 

 tree occurs in many towns of South Africa which are not 

 troubled with hay fever. The explanations suggested are the 

 hot, dry weather during the principal flowering season of the 

 pepper tree; and the fact that this tree is cultivated _ in large 

 numbers in Bloemfontein as a street and garden tree. Kimberley. 

 whose climate is like that of Bloemfontein, and which, too, has 

 many pepper trees, is also subject to these epidemics. To pre- 

 vent the epidemics, the removal of the male pepper tree is 

 recommended. Other causes of pollinosis and of hay fever 

 symptoms in Bloemfontein are mentioned. 



