INTRODUCTORY ESSAY. XIX 
evidence in the fact that, in the meridians of Australia and Japan, we have, first, the north-west 
coast of Australia sinking, together with the Louisiade Archipelago to its north; then, approaching 
the Line, the New Ireland group is sinking, as are also the Caroline Inlands, in lat. J 
this, however, in lat. 15° N., are the Marianne Islands (rising), of whose vegetation nothing is 
known; in 27° N., the Bonin Islands (also rising); and in 80° N. is Japan, with which this bota- 
nical relationship exists. 
It is objected by Mr. Darwin to this line of argument (as to that at p. xv concerning the 
Pacific Islands), that all these sinking areas are volcanic islandSj having no traces of older rocks on 
them ; but I do not see that this altogether invalidates the hypothesis, for many of the loftiest moun- 
tains throughout the Malayan Archipelago, New Zealand, and the Pacific Islands, arc volcanic; some 
are active, and many attain 10-1-1,000 feet in elevation, whilst the lower portions of some of the 
largest of these islands are formed of rocks of various ages. 
On the General Phenomena of the Distribution of Plants in Time. 
A third class of facts relates to the antiquity of vegetable forms and types on the globe, as evi- 
denced by fossil plants. The chief facts relating to these are the following : — 
31. The earliest Flora of which we know much scientifically, is that of the Carboniferous forma- 
tion. We have indeed plants that belonged to an earlier vegetation, but they do not differ in any 
important respects from those of the carboniferous formation. 
Now the ascertained features of the coal vegetation may be summed up very briefly. There 
existed at that time, — 
Filices ; in the main entirely resembling their modern representatives, and some of which may 
even be generically, though not specifically, identical with them. 
Lycopodiacece ; the same in their main characters as those now existing, and, though of higher 
specialization of stem, of greater stature, of different species, and perhaps also genera, from modern 
Lycopodiacece, yet identical with these in the structure of their reproductive organs and their con- 
tents, and in the minute anatomy of their tissues. 
Conifera. The evidence of this Order is derived chiefly from the anatomical characters of the 
Dicotyledonous wood so abundantly found in the coal, and which seems to be identical in all impor- 
tant respects with the wood of modern genera of that Order, to which must be added the probability 
of Trigonocarpon and Nwggerathia being Gymnospermous, and allied to Salisburia* On the other 
hand, it must not be overlooked that no Coniferous strobili have been hitherto detected in the Car- 
boniferous formation. 
Cycadete. Some fragments of wood, presenting a striking similarity in anatomical characters 
to that of Cycadece, have been found in the carboniferous series. 
In the absence of the fructification of Catamites, Calamodendron, Halonia, Anabathra, etc., 
there are no materials for any safe conclusions as to their immediate affinities, beyond that they all 
seem to be allied to Ferns or Lycopodiacece ; but the same can hardly be said of the affinities of 
Volkmannia,f Antholithes and others, which have been referred, with more or less probability, to 
Angiospermous Dicotyledons. 
The Permian Flora is for the most part specifically distinct from the Carboniferous, but many of 
* Phil. Trans. 1855, p. 149. f See Quarterly Journal of Geological Society, May, 1854. 
