LUTHER BURBANK 
If this is not absolutely clear, you will do well 
to re-read the above paragraphs, and it is quite 
worth your while to consider the matter somewhat 
attentively. 
If you have only theoretical interest in plant 
breeding you should be concerned in the matter 
no less personally, because the same laws of hered- 
ity that are about to be illustrated apply with full 
force to all life, including human offspring. 
If, on the other hand, you have thought of un- 
dertaking some experiments in plant developing, 
which I hope is the case, it is doubly important 
that you should get the full significance of these 
simple formule. Like other formule, they are 
devised solely for convenience in promulgating 
ideas. As used in the following illustration, they 
will make it possible to present vividly the case of 
our black-sheep cherry, and through this to clarify 
a large number of obscure cases that must prove 
very puzzling to the novitiate in plant develop- 
ment. 
EXPLAINING THE BLACK SHEEP 
Let us now stake our way, as it were, with the 
aid of the upper-case and lower-case letters, along 
the line of a series of plant experiments through 
which a certain patrician cherry was developed. 
To avoid complications and to escape getting into 
a tangle of ideas and a maze of letters, let us con- 
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