Medical Officers of the Army of India.

69

highly specialized, and which prepares the way for a more highly specialized
phanerogamic flora. But the larger proportion of the phanerogams that do
reach such islands are ocean-distributed and littoral species that cannot ascend
beyond a certain height, those whose fruits or seeds are adapted for very dis-
tant wind-conveyance being comparatively few in number, and the proportion
of such fruits or seeds that escape from perishing in the ocean en route being
very small. Hence, in such islands the proportion of cryptogams to phanero-
gams always remains high, and is increased in a direct ratio with the distance
of the island from adjacent land, and in an inverse ratio with the suitability of
the surface of the island for the support of vegetable life.

     The conditions that prevail in newly emerged coral islets are very different.
Their low elevation in itself diminishes the chances of wind-conveyed spores
alighting on them, and is in itself unfavourable for the germination of many of
the spores that do alight. Then, for those that have succeeded in alighting
and that have germinated the struggle for existence is intensified by the simul-
taneous arrival of another class of species, independently conveyed, more highly
specialized, with its individual species more largely represented, and for which
the same physical conditions are in the highest degree favourable. These
conditions appear sufficiently to explain the difference of the proportions in
Krakatau and in the Laccadives.

     In concluding, the writer wishes to acknowledge his great indebtedness to
Dr. Alcock for much information concerning the present flora of the Lacca-
dives and to Dr. King for numerous valuable suggestions while analysing its
constituents.