THE PEPPER TREE AND HAY FEVER. 527 



ley, of Manchester (himself a sufferer) have placed this beyond 

 doubt in his own case. He also showed that the pollen from 

 Pine trees is very powerful in its effect. 



But all the plants which have hitherto been shown to cause 

 the disease, are plants whose pollen is normally carried by the 

 wind; and it would be something new to science to find the 

 disease caused by pollen which is carried from flower to flower 

 by agencies other than the wind. 



Though the opinion that the Pepper Tree is the cause of our 

 epidemic Hay Fever is so widespread, it should be noted that none 

 of the evidence in favour of the opinion is convincing. It has 

 been stated that (Letter from Dr. S. M. de Kock, M.B., Ch.B., to 

 Town Clerk, December 31st, 1917) "before Pepper Trees were 

 extensively planted in Bloemfontein hay fever as an epidemic 

 was unknown ;" and that the introduction of the epidemic has 

 " followed the extensive planting of the Pepper Tree in Bethulie, 

 Kimberley and other towns." On the other hand it should be 

 noted that Pepper Trees are very plentiful in both Grahamstown 

 and Maritzburg, and yet in neither town is epidemic hay fever 

 existent. Again, though it is maintained that " the start of the 

 epidemic of hay fever is synchronous with the flowering of the 

 Pepper Trees," my observations last season showed that the male 

 trees were in flower intermittently all through the rainy season, 

 until, in fact, the first severe frost. 



Before considering some experiments with the Pepper pollen, 

 reference will be made to the aromatic principle contained in the 

 trees : 



The Pepper Tree is very rich in resin ; and American Mastic, 

 a kind of resin, is obtained from it. There is a very large resin 

 canal in the phloem of each bundle of the leaf, and one large and 

 several smaller canals in the phloem of each bundle of the stem, 

 and if either leaf or stem be injured the resin exudes as a trans- 

 lucent fluid, which gradually hardens and turns white on exposure 

 to the air. The tree itself has a pungent and irritating odour 

 which is very noticeable when working with injured portions of 

 the plant, but it is extremely improbable that under ordinary con- 

 ditions the volatile constituents of the resin are even present in 

 the atmosphere in sufficient quantity to cause hay fever. Indeed, 

 the odour is only noticeable out-of-doors within a few yards of 

 the tree. 



Experiments "mith Pepper Pollen. — Two of my colleagues, 

 Professor M. M. Rindl, D.Ing. and Professor W. Conlin, M.A., 

 who are hay-fever sufferers, were sufficiently public-spirited to 

 allow me to experiment on them to ascertain whether pollen from 

 the Pepper Tree would induce an attack of hay fever. Stamens 

 with open anthers from male flowers were collected and carefully 

 air-dried, and the material was them lightly crushed to liberate 

 the pollen grains. As a preliminary test each smelled the con- 

 tents of the bottle after the bottle had been violently shaken, 

 Neither experienced any ill-effects. If fresh pepper pollen were 

 carried in the air the conditions of the experiment were such 

 that some of the dried material would have remained in suspen- 

 sion in the air of the bottle sufficiently long to be inhaled. 



D 



