ning a
considerable degree of uniformity in morphological characters throughout
their history. The Sphenophyllales are the only other class with which
they show any relation; if such a connection existed, the common point
of origin must lie exceedingly far back.

The fossil record, as at present known, cannot, in the nature of things,
throw any direct light on what is perhaps the most disputed question in
the morphology of plants--the origin of the alternating generations of
the higher Cryptogams and the Spermophyta. At the earliest period
to which terrestrial plants have been traced back all the groups of
Vascular Cryptogams were in a highly advanced stage of evolution, while
innumerable Seed-plants--presumably the descendants of Cryptogamic
ancestors--were already flourishing. On the other hand we know
practically nothing of Palaeozoic Bryophyta, and the evidence even for
their existence at that period cannot be termed conclusive. While
there are thus no palaeontological grounds for the hypothesis that the
Vascular plants came of a Bryophytic stock, the question of their actual
origin remains unsolved.

III. NATURAL SELECTION.

Hitherto we have considered the palaeontological record of plants in
relation to Evolution. The question remains, whether the record
throws any light on the theory of which Darwin and Wallace were the
authors--that of Natural Selection. The subject is clearly one which
must be investigated by other methods than those of the palaeontologist;
still there are certain important points involved, on which the
palaeontological record appears to bear.

One of these points is the supposed distinction between morphological
and adaptive characters, on which Nageli, in particular, laid so much
stress. The question is a difficult one; it was discussed by Darwin
("Origin of Species" (6th edition), pages 170-176.), who, while
showing that the apparent distinction is in part to be explained by our
imperfect knowledge of function, recognised the existence of important
morphological characters which are not adaptations. The following
passage expresses his conclusion. "Thus, as I am inclined to believe,
morphological differences, which we consider as important--such as
the arrangement of the leaves, the divisions of the flower or of the
ovarium, the position of the ovules, etc.--first appeared in many cases
as fluctuating variations, which sooner or later became constant through
the nature of the organism an