PEPPER TREE AS A CAUSE OF HAY FEVER. 



181 



With a view to throwing light on this difficulty, pollen 

 plates were exposed in Kimberley, Grahamstown, Maritzburg and 

 Johannesburg when the pepper tree was in flower, and informa- 

 tion was collected regarding the number and density of their 

 pepper trees, for comparison with similar data from Bloemfon- 

 tein. 



(a) Number of Pepper Trees in Various Toicns and Their 

 Density. 



Steps were taken to count the number of pepper trees on 

 measured areas of the five towns under comparison, and the 

 following are the results: — 



Ttl 



Ttl 



All the areas in these two towns were blocks of streets 

 except the last one in the Bloemfontein list, which includes only 

 a single street (Aliwal Street). The three first-named areas in 

 each town were selected as areas of average density (in parts of the 

 town where the tree occurs), the others representing dense areas. 

 In view of the fact that the areas in which the trees were 

 counted form only a small fraction of the total area planted with. 

 pepper trees, it will be seen from the table that in both towns 

 the tree is very numerous ; and the figures in the third column 

 show that in certain areas it is also very dense. 



