nd flora it might have preserved may have
been destroyed by great volcanic eruptions. Mr. Darwin collected some
masses of tufa which were found to be mainly organic, containing, besides
remains of fresh-water infusoria, the siliceous tissue of plants! In the
light of the great extent of the submarine bank on which the island stands,
Mr. Darwin's remark, that--"we may feel sure, that at some former epoch,
the climate and productions of Ascension were very different from what they
are now,"--has received a striking confirmation. (See _Naturalist's Voyage
Round the World_, p. 495.)

[123] "Notes on the Classification, History, and Geographical Distribution
of Compositae."--_Journal of the Linnean Society_, Vol. XIII. p. 563
(1873).

[124] The Melhaniae comprise the two finest timber trees of St. Helena, now
almost extinct, the redwood and native ebony.

[125] _Journal of the Linnean Society_, 1873, p. 496. "On Diversity of
Evolution under one set of External Conditions." _Proceedings of the
Zoological Society of London_, 1873, p. 80. "On the Classification of the
Achitinellidae."

[126] "Memoirs on the Coleoptera of the Hawaiian Islands." By the Rev. T.
Blackburn, B.A., and Dr. D. Sharp. _Scientific Transactions of the Royal
Dublin Society._ Vol. III. Series II. 1885.

[127] See Hildebrand's _Flora of the Hawaiian Islands_, Introduction, p.
xiv.

[128] _Flora of the Hawaiian Islands_, by W. Hildebrand, M.D., annotated
and published after the author's death by W. F. Hildebrand, 1888.

[129] These are obtained from Hildebrand's _Flora_ supplemented by Mr.
Bentham's paper in the _Journal of the Linnean Society_.

[130] Among the curious features of the Hawaiian flora is the extraordinary
development of what are usually herbaceous plants into shrubs or trees.
Three species of Viola are shrubs from three to five feet high. A shrubby
Silene is nearly as tall; and an allied endemic genus, Schiedea, has
numerous shrubby species. _Geranium arboreum_ is sometimes twelve feet
high. The endemic Compositae are mostly shrubs, while several are trees
reaching twenty or thirty feet in height. The numerous Lobeliaceae, all
endemic, are mostly shrubs or trees, often resembling palms or yuccas in
habit, and sometimes twenty-five or thirty feet high. The only native genus
of Primulaceae--Lysimachia--consists mainly of shrubs; and even a plantain
has a woody stem sometimes six feet high.

[131] _Geological Magazine_, 1870, p. 155.