Africa, showing a similar
Asiatic preponderance to what is said to occur in Madagascar. With the
genera, however, the proportions are different, for I find by going through
the whole of the generic distributions as given by Mr. Baker, that out of
the 440 genera of wild plants fifty are endemic, twenty-two are Asiatic but
not African, while twenty-eight are African but not Asiatic. This implies
that the more ancient connection has been on the side of Africa, while a
more recent immigration, shown by identity of species, has come from the
side of Asia; and it is already certain that when the flora of Madagascar
is more thoroughly worked out, a still greater African preponderance will
be found in that island.

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A few Mascarene genera are found elsewhere only in South America,
Australia, or Polynesia; and there are also a considerable number of genera
whose metropolis is South America, but which are represented by one or more
species in Madagascar, and by a single often widely distributed species in
Africa. This fact throws light upon the problem offered by those mammals,
reptiles, and insects of Madagascar which now have their only allies in
South America, since the two cases would be exactly parallel were the
African plants to become extinct. Plants, however, are undoubtedly more
long-lived specifically than animals--especially the more highly organised
groups, and are less liable to complete extinction through the attacks of
enemies or through changes of climate or of physical geography; hence we
find comparatively few cases in which groups of Madagascar plants have
their _only_ allies in such distant regions as America and Australia, while
such cases are numerous among animals, owing to the extinction of the
allied forms in intervening areas, for which extinction, as we have already
shown, ample cause can be assigned.

_Curious Relations of Mascarene Plants._--Among the curious affinities of
Mascarene plants we have culled the following from Mr. Baker's volume.
Trochetia, a genus of Sterculiaceae, has four species in Mauritius, one in
Madagascar, and one in the remote island of St. Helena. Mathurina, a genus
of Turneraceae, consisting of a single species peculiar to Rodriguez, has
its nearest ally in another monotypic genus, Erblichia, confined to Central
America. Siegesbeckia, one of the Compositae, consists of two species, one
inhabiting the Mascarene islands, the other Peru. Labourdonasia, a genus of
Sapotace