PEPPER TREE AS A CAUSE OF HAY FEVER. 191 



XIV. Prevention Recommended. 



There is no satisfactory cure for hay fever; besides preven- 

 tion is better. The removal of the male pepper tree, the plant 

 that produces the toxic pollen, is recommended. It is fortunate 

 that the cause of these epidemics is not a native plant occurring 

 in large quantities in the veld, nor one which for any other 

 reason it would be impracticable to remove. 



An alternative is immunisation with a vaccine prepared from 

 the pollen. But this would entail considerable inconvenience and 

 expense to patients; would almost certainly mean an annual 

 series of injections ; and, even then, could not be relied upon to 

 confer complete immunity. It would also be necessary, in the 

 first instance, to arrange for the preparation of a vaccine, which 

 would probably present some difficulty. According to Dr. 

 Scheppegrell, extensive experience in America has shown that no 

 method of dealing with hay fever, other than the removal of the 

 pollen-producing plant, has given satisfactory results. 



During the summer, the sex of the pepper tree can be 

 recognised by the character of the flowers ; and in winter by the 

 fact that only the female tree bears " berries." The distinguish- 

 ing character of the flowers of the male tree is the presence of 

 golden yellow pollen in the anthers ; whilst in the flowers of the 

 female tree, the anthers are empty (sterile) and white in colour. 

 In Bloemfontein the two sexes are about equal in number. It 

 should be pointed out that, although the terms " male " and 

 "female " have been used in describing the trees, this has been 

 done as a matter of convenience and is not strictly accurate. 

 Some male trees bear a few female flowers which, incidentally, 

 foiTn fruits. 



Though experience has shown that several other varieties 

 of street trees grow fairly well in Bloemfontein, attention has 

 been given to the practicability of putting a female top on to the 

 trunks of male pepper trees, and of obtaining, for planting out, 

 young pepper trees which could be relied upon to bear only 

 female flowers. 



To replace male trees by small seedlings would be a gamble 

 as far as the sex is concerned, as this cannot at present be 

 recognised until the tree flowers. There is probably some trifling 

 difference in the male and female seedlings by which the sex 

 could be distinguished, even at a very early age, but a reliable 

 character has not yet been observed. At present the only certain 

 method of obtaining female trees from seedlings would be to 

 delaj' planting out until the flowers appear. 



Cuttings from a female plant would produce only female 

 trees ; hence experiments have been made to test the practic- 

 ability of propagating the female tree from cuttings. Attempts 

 have also been made to graft or bud a female top on to a male 

 trunk, as well as to insert buds from a female plant on to seed- 

 lings. If practicable, this latter step would ensure that all seed- 

 lings would bear a female top. The experiments were performed 

 at the College and also repeated independently by Mr. A. 



