rickly side which
drought and heat aggravate. In the North our thistles and thorns and
spines are a milder expression of this mood. The spines on the
blackberry-bush tend against its propagation for the same reason. Among
our wild gooseberries, there are smooth and prickly varieties, and one
succeeds about as well as the other. Apple-and pear-trees in rough or
barren places that have a severe struggle for life, often develop sharp,
thorny branches. It is a struggle of some kind which begets something
like ill-temper in vegetation--heat and drought in the desert, and
browsing animals and poor soil in the temperate zones. The devil's club
in Alaska is one mass of spines; why, I know not. It must just be
original sin. Our raspberries have prickles on their stalks, but the
large, purple-flowering variety is smooth-stemmed.

Mr. John C. Van Dyke in his work on the desert expresses the belief that
thorns and spines are given to the desert plants for protection; and
that if no animal were there that would eat them, they would not have
these defenses. But I believe if there had never been a browsing animal
in the desert the cacti would have had their thorns just the same.

Nature certainly arms her animal forms against one another. We know the
quills of the porcupine are for defense, and that the skunk carries a
weapon that its enemies dread, but I do not believe that any plant form
is armed against any creature whose proper food it might become. Cacti
carry formidable weapons in the shape of spines and thorns, but the
desert conditions where they are found, heat and aridity, are no doubt
their primary cause. The conditions are fierce and the living forms are
fierce.

We cannot be dogmatic about Nature. From our point of view she often
seems partial and inconsistent. But I would just as soon think that
Nature made the adobe soil in the arid regions that the human dwellers
there might have material at hand with which to construct a shelter, as
that she gives spines and daggers to any of the vegetable forms to
secure their safety. One may confute Mr. Van Dyke out of his own mouth.
He says:

Remove the danger which threatened the extinction of a
family, and immediately Nature removes the defensive
armor. On the desert, for instance, the yucca has a thorn
like a point of steel. Follow it from the desert to the
high tropical table-lands of Mexico where there is plenty
of soil and moisture, plenty of chance for yucca