230 
Journal of Agricultural Research 
Vol. II, No. 3 
tion is that which results in prevention. To illustrate this point the 
present conditions in the State of Florida may be cited. An examination 
of Florida orchards seems to indicate that the parasite is not yet widely 
distributed in that State; in fact, it has been found in only one locality. 
If henceforth all nursery stock in Florida is examined for T. semipenetrans 
and no stock is accepted for shipment or planted out unless upon inspec¬ 
tion it is found free from this nematode, very much can probably be 
done to limit the spread of disease. 
Hitherto no information has come to light that shows any particular 
kind of Citrus stock to be more resistant than others. The Tylenchulus 
has been found to occur upon the following stocks: Sour orange, sweet 
orange, grapefruit, and Citrus irifoliata . Investigations are under way 
with the object of ascertaining whether these stocks vary among them¬ 
selves in resistance to the Tylenchulus and whether it is possible to 
discover a thoroughly resistant stock. 
During the life-history studies it was discovered that hot water is fatal 
to Tylenchulus semipenetrans , and that Citrus roots survive the tempera¬ 
ture required to kill the Tylenchulus. Some of the smaller roots may be 
injured, but the larger roots are not seriously harmed, and when the 
treated trees are planted out, they proceed to grow new feeding roots. 
These facts lead to the hope that a hot-water treatment may prove to be 
a more or less efficient means of disinfection or at least prove to be a 
palliative. 
