FLORIDA .STATE HORTICULTURAL SOCIETY. 
39 
plant should be found that does success¬ 
fully resist the attacks of the fly, then 
this plant should be used, by cross fertili¬ 
zation, to impart its resistant quality to 
an orange that should as well possess all 
the other qualities desirable in a good 
fruit. But suppose, you may well object, 
that such a tree could not be found. It 
is quite possible, nay, it is even very prob¬ 
able, that no species of the citrus fruit is 
completely immune to the whitefly’s at¬ 
tacks. In that case we must simply make 
it so. Another fact that is familiar to 
plant physiologists, is that when an or¬ 
ganism is subjected to repeated and long 
continued attacks of a malignant disease, 
it will eventually become immune to it by 
the formation of antitoxins in the sys¬ 
tem and this, in many cases, is transmit¬ 
ted to the offspring. The African races 
having continuously been subjected to the 
attacks of the malaria germ, the negroes, 
even of our own country, are largely im¬ 
mune to this disease. The Hebrew race 
offers great resistance to tuberculosis be¬ 
cause it has been subjected to attacks of 
this disease much longer than any other 
European people, and because tuberculo¬ 
sis appeared in Ireland long after it had 
become prevalent in other parts of Eu¬ 
rope, the Irish are more subject to its at¬ 
tacks than any other white race. We are 
all familiar with the efficacy of vaccina¬ 
tion in suppressing smallpox and of the 
use of antitoxins in the treatment of diph¬ 
theria and hydrophobia. But what has 
this to do, you may ask, with the immu¬ 
nizing of the orange to the attacks of the 
whitefly? Nothing, except that it points 
the way by which we may successfully 
cope with this peculiar trouble. 
Taking into account the fact that na¬ 
ture provides a natural remedy for dis¬ 
ease by gradually eliminating the weak 
and preserving the strong so that she 
may evolve a vigorous and healthy race, 
we would go to those orange trees that 
have longest been subjected to the white- 
fly’s attacks and from the most vigorous 
of them raise a large number of seedling 
trees. These, when they had arrived at 
a reasonable age, should be infected with 
the whitefly and from those that most 
successfully resisted the insect other seed¬ 
ling should be grown. This process of 
infection and elimination would possibly 
have to be carried on for a number of 
generations in order that the cumulative 
resistant effects might be realized. On 
the other hand, as almost all trees and 
plants are subject to sudden mutations,, 
it is quite possible that the desired result 
may appear in the second or third genera¬ 
tion. It is not beyond the range of prob¬ 
ability that if every infected grove in the 
State was carefully inspected more than 
one tree might be found already perfectly 
immune to the fly. I would suggest, then, 
that every orange grower in whose grove 
the whitefly has appeared should examine 
every tree to see if the resistant quality 
is apparent in any specimen. I believe, 
however, that the hope of producing a 
variety that shall be perfectly immune lies, 
in breeding from infected trees and con¬ 
tinuing the process until the resistant 
strain appears. This process offers little 
consolation to you of today, but if it 
should take fifty years to bring it about 
it will be well worth all the time, the la¬ 
bor and expense that may be expended 
on it. 
