The Truth of Evolution . 201 
: the last section of this essay) or must still rely on Darwin’s explana- 
tion 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'. 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? 
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 relation of the 
Angiosperms to the Gymnosperms, on that of the Seed-plants gener- 
ally to the Ferns, and ‘on the interrelations between the various 
classes of the higher Cryptogams. 
That the fossil record has not done still more for Evolution is due 
to the fact that it begins too late—a point on which Darwin laid 
stress’ and which has more recently been elaborated by Poulton‘. 
An immense proportion of the whole evolutionary history lies behind © 
the lowest fossiliferous rocks, and the case is worse for plants than - 
for animals, as the record for the former begins, for all practical 
purposes, much higher up in the rocks. 
It may be well here to call attention to a question, often over- 
looked, which has lately been revived by Reinke®. As all admit, 
1 Trans. Royal Soc. Edinburgh, Vol. 45, Pt. 1. 1907, Vol. 46, Pt. 1. 1908, Vol. 46, 
Pt. 1m, 1909. 
2 See Seward and Gowan, ‘*The Maidenhair Tree (Ginkgo biloba),” Annals of Botany, 
Vol. xv. 1900, p. 109; also A. Sprecher, Le Ginkgo biloba L., Geneva, 1907. 
3 Origin of Species (6th edit.), p. 286. 
‘ Essays on Evolution, pp. 46 et seq., Oxford, 1908. 
* Reinke, loc. cit. p. 13. 
