60 ORIGIN OF DOMESTIC PLANTS. 
The only satisfactory proof that a given wild plant is identical 
with a given garden or field vegetable, is the test of experi- 
ment, the actual growing of the one from the seed of the other, 
or the conversion of the one into the other by transplantation 
and change of conditions.* It is hardly contended that any of 
the cereals or other plants important as human aliment, or 
as objects of agricultural industry, exist and propagate them- 
selves uncultivated in the same form and with the same pro- 
perties as when sown and reared by human art.t In fact, 
the cases are rare where the identity of a wild with a domes- 
ticated plant is considered by the best authorities as conclu- 
sively established, and we are warranted in affirming of but 
few of the latter, as a historically known or experimentally 
macrocarpa, possibly be so increased in size as to serve nearly all the purposes 
of animal ivory now becoming so scarce? Might not the various milk-pro- 
ducing trees become, by cultivation, a really important source of nutriment 
to the inhabitants of warm climates? In short, there is room to hope incal- 
culable advantage from the exercise of human skill in the improvement of 
yet untamed forms of vegetable life. 
* The poisonous wild parsnip of New England has been often asserted to be 
convertible into the common garden parsnip by cultivation, or rather to be 
the same vegetable growing under different conditions, and it is said to be de- 
prived of its deleterious qualities simply by an increased luxuriance of growth 
in rich, tilled earth. Wild medicinal plants, so important in the rustic mate- 
ria medica of New England—such as pennyroyal, for example—are generally 
much less aromatic and powerful when cultivated in gardens than when self- 
sown on meagre soils, On the other hand, the eznchona, lately introduced 
from South America into British India and carefully cultivated there, is found 
to be richer in quinine than the American tree. 
+ Some recent observations of Wetzstein are worthy of special notice, 
“The soil of the Haurin,” he remarks, ‘‘ produces, in its primitive condition, 
much wild rye, which is not known as a cultivated plant in Syria, and much 
wild barley and oats. These cereals precisely resemble the corresponding cul- 
tivated plants in leaf, ear, size, and height of straw, but their grains are sen- 
sibly flatter and poorer in flour.”"—Retsebericht iiber Haurin und die Tracho- 
nen, p. 40. 
Some of the cereals are, to a certain extent, self-propagating in the soil 
and climate of California. ‘‘ Volunteer crops are grown from the seed which 
falls out in harvesting. Barley has been known to volunteer five crops in suc- 
cession,””—-PRAYER-FROWD, Six Months in California, p. 189. 
