s the dog,
which had all been wisely preserved during their long voyage. The
Polynesians are so frequently lost on the ocean, that this degree of
prudence would occur to any wandering party: hence the early colonists of
New Zealand, like the later European colonists, would not have had any
strong inducement to cultivate the aboriginal plants. According to De
Candolle we owe thirty-three useful plants to Mexico, Peru, and Chile; nor
is this surprising when we remember the civilized state of the inhabitants,
as shown by the fact of their having practised artificial irrigation and
made tunnels through hard rocks without the use of iron or gunpowder, and
who, as we shall see in a future chapter, fully recognised, as far as
animals were concerned, and therefore probably in the case of plants, the
important principle of selection. We owe some plants to Brazil; and the
early voyagers, namely Vespucius and Cabral, describe the country as
thickly peopled {312} and cultivated. In North America[534] the natives
cultivated maize, pumpkins, gourds, beans, and peas, "all different from
ours," and tobacco; and we are hardly justified in assuming that none of
our present plants are descended from these North American forms. Had North
America been civilized for as long a period, and as thickly peopled, as
Asia or Europe, it is probable that the native vines, walnuts, mulberries,
crabs, and plums, would have given rise, after a long course of
cultivation, to a multitude of varieties, some extremely different from
their parent-stocks; and escaped seedlings would have caused in the New, as
in the Old World, much perplexity with respect to their specific
distinctness and parentage.[535]

_Cerealia._--I will now enter on details. The cereals cultivated in
Europe consist of four genera--wheat, rye, barley, and oats. Of wheat
the best modern authorities[536] make four or five, or even seven
distinct species; of rye, one; of barley, three; and of oats, two,
three, or four species. So that altogether our cereals are ranked by
different authors under from ten to fifteen distinct species. These
have given rise to a multitude of varieties. It is a remarkable fact
that botanists are not universally agreed on the aboriginal parent-form
of any one cereal plant. For instance, a high authority writes in
1855,[537] "We ourselves have no hesitation in stating our conviction,
as the result of all the most reliable