The greater number of Australian genera, except the Acotyledonous, differ from those of Europe; there are, however, a few European genera, as Utricularia, Drosera, and Samolus, that appear to have even their maximum in Terra Australis.
From the following list of species, common to Terra Australis and Europe, I have carefully excluded all such, as though now existing in the different Settlements, have evidently, or probably, been introduced, and I am satisfied that no naturalized plant will be found in it except, perhaps, Cynodon Dactylon.
I have also excluded certain plants, as Elatine Hydropiper, Geum urbanum, Oxalis corniculata, Lycopus europæus, and Typha angustifolia, which, though appearing to differ in some respects from those of Europe, are probably not specifically distinct. And if among the Phænogamous plants inserted there be any room for doubt respecting the identity of the Australian and European species, it may possibly be as to Arenaria marina, Zapania nodiflora, Atriplex Halimus, Potamogeton gramineum, Cyperus rotundus, and Holcus gryllus.
The first observation that occurs with regard to this list is, that the relative proportions of the three primary divisions of plants compared with those of the Australian Flora are inverted: for of 2900 Dicotyledones of the Flora only 15 are natives of Europe; while of 860 Monocotyledones 30, and of 400 Acotyledones upwards of 120 appear in the list.
The Phænogamous plants of the list are, with very few exceptions, also natives of North America, and several of them are found even in other parts of the world.
There is nothing peculiar in the apparent structure or œconomy of the Dicotyledonous plants common to countries so remote to account for their more general diffusion: though several of them grow in wet or marshy ground, yet very few are properly aquatic plants; and in the structure of their seeds the only circumstance in which they all agree is in the plumula of their embryo not being evolved.
Of the Monocotyledones, on the other hand, a considerable number are aquatic plants; and the greater part of those that are not aquatic belong to the irregular tribes, supposed to have a simpler structure.
Among the Acotyledonous or Cryptogamous orders it is remarkable