tioned in our own day, it is desirable to assure ourselves how the
case stands, and in particular how far the evidence from fossil plants
has grown stronger with time.

As regards direct evidence for the derivation of one species from
another, there has probably been little advance since Darwin wrote, at
least so we must infer from the emphasis laid on the discontinuity
of successive fossil species by great systematic authorities like
Grand'Eury and Zeiller in their most recent writings. We must either
adopt the mutationist views of those authors (referred to in the last
section of this essay) or must still rely on Darwin's explanation of the
absence of numerous intermediate varieties. The attempts which have been
made to trace, in the Tertiary rocks, the evolution of recent species,
cannot, owing to the imperfect character of the evidence, be regarded as
wholly satisfactory.

When we come to groups of a somewhat higher order we have an interesting
history of the evolution of a recent family in the work, not yet
completed, of Kidston and Gwynne-Vaughan on the fossil Osmundaceae.
("Trans. Royal Soc. Edinburgh", Vol. 45, Part III. 1907, Vol. 46, Part
II. 1908, Vol. 46, Part III. 1909.) The authors are able, mainly on
anatomical evidence, to trace back this now limited group of Ferns,
through the Tertiary and Mesozoic to the Permian, and to show, with
great probability, how their structure has been derived from that of
early Palaeozoic types.

The history of the Ginkgoaceae, now represented only by the isolated
maidenhair tree, scarcely known in a wild state, offers another striking
example of a family which can be traced with certainty to the older
Mesozoic and perhaps further back still. (See Seward and Gowan, "The
Maidenhair Tree (Gingko biloba)", "Annals of Botany", Vol. XIV. 1900,
page 109; also A. Sprecher "Le Ginkgo biloba", L., Geneva, 1907.)

On the wider question of the derivation of the great groups of plants,
a very considerable advance has been made, and, so far as the higher
plants are concerned, we are now able to form a far better conception
than before of the probable course of evolution. This is a matter
of phylogeny, and the facts will be considered under that head; our
immediate point is that the new knowledge of the relations between the
classes of plants in question materially strengthens the case for the
theory of descent. The discoveries of the last few years throw light
especially on the relati