I't2 PEPPEK TREE AS A CAUSE OF HAY FEVER. 



Cliisholni (who is in charge of the local Government Gardens) in 

 conjunction with the Forestry Department; and by Mr. F. Griffiths, 

 Superintendent of Parks. All gave negative results, except that 

 Mr. Chisholm succeeded in the budding experiments in inducing 

 buds to take, but found that the continued production of shoots 

 from the stock, whether old or that of a seedling, gave so much 

 trouble as to make the method valueless in practice. Regulated 

 bottom heat was not available in any of the attempts to strike 

 the cuttings. 



XV. Dust. 



Although more dust than pepper tree pollen was found on 

 the pollen plates exposed in Bloemfontein, there is convincing 

 evidence that dust is not the cause of the hay fever epideinics, in 

 that, in some seasons, duststorms are frequent from July onwards, 

 and 3^et it is only after the pepper tree comes into flower that 

 hay fever commences. But it is probable that both the dustiness 

 and dryness of the air of Bloemfontein predispose to and 

 aggravate hay fever by making the mucous membranes more 

 sensitive (Stuart-Low, 1919). 



Dust is usually prevalent in Bloemfontein from August until 

 the heavy summer rains begin. It is to be attributed to high 

 winds at a season when the surface of the ground is bare, dry and 

 powdery. The dusty winds at Bloemfontein are westerly. The 

 worst duststorms are of the whirlwind type, in which the dust can 

 be seen to be churned about, and whose onward march can be 

 followed from long distances. As this kind of wind carries dust 

 for many miles, preventive measures are impracticable. But dust- 

 ^^torms of this type are fortunately rare. On most dusty days the 

 wind probably blows more or less horizontally, and it can be 

 noticed that much of the dust is carried only a short distance at 

 one flight, to be dropped and picked up again by a succeeding 

 gust. The chief sources of the dust carried into town by such 

 winds are the bare veld (due to heavy grazing) and unmade tracks 

 used by traffic at the sides of roads. Whether it is economically 

 practicable to prevent this dust being carried into town could 

 only be settled by trial (careful regulation of grazing on the town 

 lands, tree planting, etc.). The evidence of enclosed and 

 imgrazed, or lightly grazed areas, in and around Bloemfontein. 

 sjiows that, despite a reduced rainfall in recent years, the climate 

 is still capable of producing a sufficiently dense growth of vegeta- 

 tion to retain dust dropped into it from the wind. There are also 

 fruitfid soiu'ces of dust within the town itself. 



XVI. Other Causes of Hay Fever in Bloemfontein. 



There are many other causes of hay fever (pollinosis) and 

 hay fever symptoms in and near Bloemfontein, in addition to the 

 pollen of the pepper tree. The probable causes to which my 

 attention has been called in the course of this investigation are : 

 emanations from horses and cows (animal asthmas); eating 

 grapes and melons (food idiosyncrasies) ; pollen of grass and 

 certain weeds; pollen (or scent?) of various cultivated plants. 



