108 PEPPER TREE AS A CAUSE OF HAY FEVER. 



to be in th,e air. It must, tlierefore, have been inhaled by every- 

 one, whether susceptible or immune. What is, perhaps, at least 

 as important is that no other variety of pollen was found in these 

 secretions, and had they occurred they would probably have been 

 detected, as the majority of pollens have spicules or other mark- 

 ings by which they can be identified whether unswoUen or burst. 

 These examinations were made in December, 1920, and the only 

 pollen found on pollen plates at the time was that of th,6 pepper 

 tree . 



VI. Sterility of Pepper Tree Pollex. 



Careful bacteriological examination of the flowers of the male 

 pepper tree by Mr. O. F. Gibbs, Bacteriologist in the Public 

 Health Department, showed the interior of the unopened flower 

 buds, including the pollen, to be bacteriologically sterile. The 

 pollen, therefore, plays no special part in introducing the bac- 

 teria found in the nasal discharge of patients suffering from hay- 

 fever. {Vide Potts, 1919.) 



VII. Shape axd Size of Pepper Tree Pollen. 



The pollen grains of the pepper tree are oval in outline with 

 somewhat trimcate ends, and have a smooth surface, free from 

 spines or other outgrowths. Their most conspicuous feature is a 

 prominent groove running along one side. In general shape they 

 bear a striking resemblance to a grain of wheat. Their size varies 

 as a rule between 33 to 37 microns long by 14 to 18 microns 

 broad, most of them being of the order 33 microns long by 17 

 microns broad. It should be noted that pepper tree pollen is 

 somewhat larger than the majority of pollens that have been 

 found to cause hay fever elsewhere. 



VIII. POLLIXATIOX OF THE FlOWERS OF THE PePPER TrEE. 



It has already been explained that the flowers of both male 

 and female trees produce nectar in abundance, and that the 

 pollen (in newly-opened flowers) and stigma are sticky. These 

 characters and the showy corolla would lead one to expect pol- 

 lination by animals. Insects, especially flies, frequent the 

 flowers. Some insects caught visiting the flow.ers were identified 

 at the South African Museum, Capetown, by the courtesy of the 

 Dii'ector, Dr. L. Peringuey, as follows: — 



Musca domestica L. — The common house fly. 



Paratrycyclea stahnlans Bez. — A fly. ' 



Chortophila ciUcrura Eond. — A syi"phid fly. 



Dacus hinotatus Loew. — A fruit fly. 



Stomoxijs calcitrans L. — Stable fly. 



A Ceratitid (Fruit) fly. 



Xanthogramma (egyptium Wied. — A wasp. 



Apis mcWifica var andersoni Higs. — Honey bee. 



