ain, while the Oriental flora is
represented by a good many species. Lusitanian species have spread
chiefly southward into North Africa, and northward into France, the
British Islands, and even Scandinavia. As I have mentioned in the third
chapter, there are a good many species of Lusitanian origin in the
British Islands. However, we have only a mere remnant of what we ought
to have, had the climate been less trying. It is probable, too, that the
submergence destroyed a good many plants and the insects dependent on
them. That the Lusitanian fauna is very ancient in the British Islands
is proved by the fact of the discontinuous distribution of so many
species. A greater number survived in Ireland than in England.

[Illustration: Fig. 20.--The Strawberry-tree (_Arbutus unedo_) in its
native habitat in the south-west of Ireland. (From a photograph by
Robert Welch.)]

[Illustration: Fig. 21.--The Irish Spurge (_Euphorbia hiberna_) in its
native habitat in the south of Ireland. (From a photograph by Robert
Welch.)]

Altogether--and this was strongly urged by Edward Forbes--the Lusitanian
element is the oldest of the components of our fauna, and it must have
poured into the British Islands for many geological periods almost
without cessation. The same author, in his classic essay, refers
especially to the Lusitanian flora, two prominent members of which are
the British plants, _Arbutus unedo_ (Fig. 20, p. 305) and _Euphorbia
hiberna_ (Fig. 21, p. 306). The former has a wide range in the
Mediterranean region, and occurs in the British Islands only in the
south-west of Ireland. The Spurge, on the other hand, is also found in
the south-west of England, besides Ireland and Southern Europe.

SUMMARY OF CHAPTER VII.

The term "Lusitanian" is in this chapter employed in the wide sense, as
indicating the South-west of Europe and North-western Africa. From this
centre, and probably also from a now sunken land which lay to the west
of it, issued a fauna and flora of which we have abundant evidence in
our own islands, especially in Ireland. Edward Forbes held that the
Lusitanian element of the British flora was of miocene age, and that it
survived the Glacial period in this country.

At the time when the Straits of Gibraltar did not exist, and when there
was free land communication between Asia Minor, Greece, and Tunis, many
Oriental species migrated westward by this ancient Mediterranean route
as far as Spain. They would then