PEPPER TREE AS A CAUSE OF HAY FEVER. 



171 



had under observation during the first half of December, 1920. 

 But on the 15th of the month there was a very slight shower 

 (0-26 inch was recorded half a mile off), not sufficient to moisten 

 the soil deeper than one quarter of an inch, yet on the 17th open 

 male flowers were again being shed in profusion, and the ground 

 was sprinkled with them to the extent of a thick seeding. 



Table XI 



^Meteorological Observatioxs : Bloemfoxtein, 1921. 



The weather records for this period will be found in Table 

 XI, but it should be remembered that the readings are taken at 

 8.30 a.m., before the dry westerly wind springs up. The fact 

 that such a small quantity of rain can result in the opening and 

 shedding of the flowers would suggest that the moistness of the 

 atmosph.ere, rather than the supply of water to the roots, is the 

 controlling factor. Experiments with cut shoots placed under 

 bell glasses, tlie humidity of the air in which was regulated, 

 showed that a very dry atmosphere prevents the flower buds 

 from opening, and that a moist and even saturated atmosphere 



