"better adapted to the existing conditions." Darwin points out (Ibid. page
279.) that species have remained unchanged for long periods, probably
longer than the periods of modification, and only underwent change when the
conditions of their life were altered. Higher organisation, judged by the
test of success, is thus purely relative to the changing conditions, a fact
of which we have a striking illustration in the sudden incoming of the
Angiosperms with all their wonderful floral adaptations to fertilisation by
the higher families of Insects.

II. PHYLOGENY.

The question of phylogeny is really inseparable from that of the truth 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.