PEPPER TREE AS A CAUSE OF HAY FEVER. 173 



X. Toxicity of the Leaves and Flowers of the Pepper Tree. 



Owing to the dry climate of Bloemfontein, and to tlxe fact 

 that the pepper tree sheds its leaves continually through the dr^- 

 season, the power of the leaves and flowers (whose falling has 

 already been referred to) to cause hay fever becomes of import- 

 ance. In a moister climate these organs would soon be con- 

 verted into vegetable mould and stick to the moist ground, or 

 be smothered by grass and weeds, and not find their way into 

 the air again. But in Bloemfontein, during the dry season, 

 there is not sufficient inoisture for decay to take place. The 

 flowers and leaves mei'ely become dry and brittle, are trodden 

 underfoot, and become ground down and mixed with the general 

 dust of the road. At this season, too, the surface of the ground 

 is bare and dry, so that powdered material is easily caught up 

 by the wind. 



Some of the dust on the pollen plates was of vegetable 

 origin, and although none could be identified as belonging to the 

 pepper tree, there is no reasonable doubt that this material must 

 be distributed by the wind along with mineral dust. 



The toxic principles contained in pepper tree pollen may 

 also occur in other parts of the plant; and, as the fallen leaves 

 and flowers are merely preserved dry without undergoing bac- 

 terial decomposition, it seems not unlikely that any such 

 poisonous principles present would remain unchanged. 



The toxicity of the dead leaves and flowers was tested by 

 the cutaneous test, as had been done wath the pepper tree pollen. 

 The results are shown in Table XII. 



Dead fallen leaves were collected, probably from trees cf 

 both sexes, and ground. The flowers used were from female 

 trees, to ensure the absence of pollen, and the material was 

 dried and also ground. The pollen was collected in the manner 

 already described (Potts, 1921) ; and the reactions it gave indicate 

 the susceptibility to epidemic haj^-fever, though the terms 

 " susceptible " and " non-susceptible " refer really to whether 

 the patient suffers or is free from hay fever in Bloemfontein 

 during the epidemic season. The normal saline was merely a 

 control inoculation. 



With one exception, in the case of the leaf tests, all the 

 susceptible patients who reacted to the neat pollen also reacted 

 to both leaves and flowers, though much less severely. On the 

 assumption that hay fever symptoms are induced by toxic pro- 

 teids, a reduced virulence of leaf and flower would be expected, 

 as the pollen grains contain a much larger proportion of protein 

 matter than is contained in leaf and flower, whose bulk is 

 largely made vip of cell walls, empty cells, and intercellular 

 spaces. 



The three patients who have not suffered from hay fever 

 gave no reaction except to the leaves, to which they all reacted 

 very slightly. The reaction of these patients to the leaves but 

 not to the flowers or pollen is difficult to understand. The 

 absence of a reaction to the pollen would show that they are not 



