LUTHER BURBANK 
curious series of minute oil wells laden with es- 
sential essences of no less individual quality. 
These traits, among others, mark the citrus 
fruits as constituting a highly specialized and iso- 
lated group of plants. 
It is not to be expected that any one of them 
could be hybridized with a member of any other 
family. But, on the other hand, within the bounds 
of the citrus family there is full opportunity, as I 
have already pointed out, for cross-fertilization. 
I am confident that many interesting develop- 
ments would have resulted from the hybridization 
of oranges and lemons and limes and citrons in 
my orchard had not the frost treated the tender- 
lings so harshly. Not unlikely there would have 
been developed new citrus fruits differing from 
any existing one as markedly as the plumcot dif- 
fers from apricot and plum. This, of course, is 
only matter of conjecture for the experiments were 
cut short, as already told, before they passed be- 
yond the early stages. 
Still the fact that I was able to effect hybridiza- 
tion between the various citrus fruits is highly 
suggestive and should prove stimulative to other 
workers. 
Here is a field as yet scarcely entered and one 
that offers almost unbounded possibilities. The 
orange industry is the great fruit industry of Cali- 
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