other hand the high degree of specialisation
in the southern floras and the little power the species possess of
holding their own in competition or in adaptation to new conditions
point to long-continued isolation. "An island... will prevent free
immigration and competition, hence a greater number of ancient forms
will survive." (Ibid. I. page 481.) But variability is itself subject to
variation. The nemesis of a high degree of protected specialisation is
the loss of adaptability. (See Lyell, "The Geological Evidences of the
Antiquity of Man", London, 1863, page 446.) It is probable that many
elements of the southern flora are doomed: there is, for example, reason
to think that the singular Stapelieae of S. Africa are a disappearing
group. The tree Lobelias which linger in the mountains of Central
Africa, in Tropical America and in the Sandwich Islands have the aspect
of extreme antiquity. I may add a further striking illustration from
Professor Seward: "The tall, graceful fronds of Matonia pectinata,
forming miniature forests on the slopes of Mount Ophir and other
districts in the Malay Peninsula in association with Dipteris conjugata
and Dipteris lobbiana, represent a phase of Mesozoic life which survives
'Like a dim picture of the drowned past.'" ("Report of the 73rd Meeting
of the British Assoc." (Southport, 1903), London, 1904, page 844.)

The Matonineae are ferns with an unusually complex vascular system and
were abundant "in the northern hemisphere during the earlier part of the
Mesozoic era."

It was fortunate for science that Wallace took up the task which his
colleague had abandoned. Writing to him on the publication of his
"Geographical Distribution of Animals" Darwin said: "I feel sure
that you have laid a broad and safe foundation for all future work on
Distribution. How interesting it will be to see hereafter plants treated
in strict relation to your views." ("More Letters", II. page 12.) This
hope was fulfilled in "Island Life". I may quote a passage from it which
admirably summarises the contrast between the northern and the southern
floras.

"Instead of the enormous northern area, in which highly organised
and dominant groups of plants have been developed gifted with
great colonising and aggressive powers, we have in the south three
comparatively small and detached areas, in which rich floras have
been developed with SPECIAL adaptations to soil, climate, and organic
environment, but comparatively imp