stem the tendril moves slowly, as if to gather strength, then C.~ stiffens and rises into an erect position parallel with it, and C so passes by the dangerous point; after which it comes rapidly down to the horizontal position, in which it moves until it again approaches and again avoids the impending obstacle.

Climbing plants are distributed throughout almost all the natural orders.  In some orders climbing is the rule, in most it is the exception, occurring only in certain genera.  The tendency of stems to move in circuits—­upon which climbing more commonly depends, and out of which it is conceived to have been educed—­is manifested incipiently by many a plant which does not climb.  Of those that do there are all degrees, from the feeblest to the most efficient, from those which have no special adaptation to those which have exquisitely-endowed special organs for climbing.  The conclusion reached is, that the power “is inherent, though undeveloped, in almost every plant;” “that climbing plants have utilized and perfected a widely-distributed and incipient capacity, which, as far as we can see, is of no service to ordinary plants.”

Inherent powers and incipient manifestations, useless to their possessors but useful to their successors—­this, doubtless, is according to the order of Nature; but it seems to need something more than natural selection to account for it.

XII

DURATION AND

ORIGINATION OF

Race and species—­

IMPORT OF SEXUAL REPRODUCTION

I Do Varieties wear out, or tend to wear out?

(New York Tribune, and American Journal of Science and the Arts, February, 1875)

This question has been argued from time to time for more than half a century, and is far from being settled yet.  Indeed, it is not to be settled either way so easily as is sometimes thought.  The result of a prolonged and rather lively discussion of the topic about forty years ago in England, in which Lindley bore a leading part on the negative side, was, if we rightly remember, that the nays had the best of the argument.  The deniers could fairly well explain away the facts adduced by the other side, and evade the force of the reasons then assigned to prove that varieties were bound to die out in the course of time.  But if the case were fully re-argued now, it is by no means certain that the nays would win it.  The most they could expect would be the Scotch verdict, “not proven.”  And this not because much, if any, additional evidence of the actual wearing out of any variety has turned up since, but because a presumption has been raised under which the evidence would take a bias the other way.  There is now in the minds of scientific men some reason to expect that certain varieties would die out in the long run, and this might have an important influence upon the interpretation of the facts.  Curiously enough, however, the recent discussions to which our attention has been called seem, on both sides, to have overlooked this.