CALIFORNIA CITRUS CULTURE. 49 
a deeay of the crown or stem, while the second may produce dead spots 
at any point. Tmproper soil (it should be sand, at least on top), over- 
irrigation and insufficient drainage are favorable to this disease. 
Iria, 24.—Navel or black rot, Alternaria citri, infecting 
the navel end. (After Amundsen.) 
Navel Rot (Alternaria citri). 
(Fig. 24.) 
This rot attacks only the navel orange. It is not a true parasite, and 
attacks the navel end only when it is injured in growth. It is thought 
that moisture in the navel cavity may favor the disease, as autumn rains 
seem to increase the affection. The navel is the finest winter variety 
for all around use, and its seedlessness adds to its excellence. This rot 
is one of its few drawbacks, but it is only occasionally that it becomes 
of serious importance. 
Root Rot (Oak-root Fungus, Armillaria mellea). 
(Fig. 25.) 
Where orange trees and many others replace oak trees in the foothills 
and valleys a toadstool fungus, which previously infested the roots of 
the oak, may attack and greatly injure the trees. It is common in 
California, and often serious. Mr. Earl Morris, county horticultural 
commissioner of Santa Clara County, regards it as the most serious 
pest in the orchards of his county at the present time. It spreads to 
other trees from the center of infection. Professor Smith suggests that 
in case this disease is troublesome other and more resistant trees, like 
walnuts or cherries, be grown in their stead. I have seen one case of 
4—coc 
