of the doctrine of evolution, for we cannot have historical evidence
that evolution has actually taken place without at the same time having
evidence of the course it has followed.

As already pointed out, the progress hitherto made has been rather in
the way of joining up the great classes of plants than in tracing the
descent of particular species or genera of the recent flora. There
appears to be a difference in this respect from the Animal record,
which tells us so much about the descent of living species, such as the
elephant or the horse. The reason for this difference is no doubt to be
found in the fact that the later part of the palaeontological record
is the most satisfactory in the case of animals and the least so in the
case of plants. The Tertiary plant-remains, in the great majority of
instances, are impressions of leaves, the conclusions to be drawn from
which are highly precarious; until the whole subject of Angiospermous
palaeobotany has been reinvestigated, it would be rash to venture on
any statements as to the descent of the families of Dicotyledons or
Monocotyledons.

Our attention will be concentrated on the following questions, all
relating to the phylogeny of main groups of plants: i. The Origin of the
Angiosperms. ii. The Origin of the Seed-plants. iii. The Origin of the
different classes of the Higher Cryptogamia.

i. THE ORIGIN OF THE ANGIOSPERMS.

The first of these questions has long been the great crux of botanical
phylogeny, and until quite recently no light had been thrown upon the
difficulty. The Angiosperms are the Flowering Plants, par excellence,
and form, beyond comparison, the dominant sub-kingdom in the flora of
our own age, including, apart from a few Conifers and Ferns, all the
most familiar plants of our fields and gardens, and practically all
plants of service to man. All recent work has tended to separate the
Angiosperms more widely from the other seed-plants now living, the
Gymnosperms. Vast as is the range of organisation presented by the great
modern sub-kingdom, embracing forms adapted to every environment, there
is yet a marked uniformity in certain points of structure, as in the
development of the embryo-sac and its contents, the pollination
through the intervention of a stigma, the strange phenomenon of double
fertilisation (One sperm fertilising the egg, while the other unites
with the embryo-sac nucleus, itself the product of a nuclear fusion, to
give rise to a nut