ON FACT VS. THEORY 
this family trace back to a common parentage and 
fully justify the classification of these seventy-five 
genera in a single family. 
If we were to look not at the structure, 
however, but at the seventy-five plants themselves, 
then, and only then, could we fully realize the 
wonders which environment, toying with that 
common heredity within the plant, has wrought. 
We should see, among the seventy-five brothers 
and sisters of that family if they were spread 
before us, the poisonous bitter-sweet, and the 
humble but indispensable potato; the egg plant 
and the Jerusalem cherry; the horse nettle and the 
jimson weed; the tobacco plant and the beautiful 
petunia; and the tomato itself. 
We should see seventy-five plants with original 
structural similarities, yet differing, in every other 
way, as night differs from day; and we should be 
able to trace, if we observed closely enough, the 
points at which, in the history of this family, new 
environment, oft repeated, has hardened into 
heredity, subject to the call of still newer environ- 
ment, which has not been lacking to bring it out; 
we should be able to trace out, by easy stages, 
why one branch ran to the poisonous bitter-sweet, 
another to the potato with its food product below 
the ground, another to the tomato with its 
tempting fruit displayed on vines above; another 
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