1919] Coit-Hodgson: Abnormal Shedding of Washington Navel Orange 301 



characters which became familiar with practice, it was easy to dis- 

 tinguish between various other species of Alternaria which were 

 occasionally met with. 



The specialized cells lining the stylar canal of orange flowers secrete 

 a pure white sugary mucilage which is exuded upon the stigma in a 

 rather large drop. This material is an excellent medium for the growth 

 and sporulation of Alternaria, as was determined by trial, the fungus 

 fruiting heavily in a short time on smears kept in a moist chamber. 

 In order to determine the amount of infection of blossoms in the 

 orchard, the stigmas were clipped with sterile scissors on agar plates 

 and the resulting growths examined a few days later for the charac- 

 teristic spore chains. The data secured in this way are presented in 

 tables 3 and 4. In the interior valleys 89 per cent of the stigmas were 

 infected and in coast localities 76 per cent. It is found that the air 

 generally throughout the state carries Alternaria spores in abundance. 

 In interior localities Alternaria spores were taken in 78 per cent of 

 exposures with ten centimeter agar plates ; in some places near the coast 

 in 63 per cent. It was also shown that while bees may and do carry 

 spores from one blossom to another the number of spores in the air is 

 sufficient to cause widespread infection without the aid of bees. 



In this connection the question naturally arises as to why. if the 

 infection of the stigmas near the coast is as great as 76 per cent, there 

 is such a relatively small number of black rot oranges. The reason 

 apparently lies in the fact that the average configuration of the navels 



