168 BOTANY OF CONGO.
the intratropical part of New Holland; their transportation to or from which cannot be supposed to have been affected in any of the ways suggested.
The probability, however, of these modes of transporta- tion, with respect to the plants referred to, and others of similar structure, being even admitted, the greater part of the lists would still remain; and to account for the disper- 481] sion of these, recourse must be had to natural causes, or such as are unconnected with human agency. But the necessity of calling in the operation of these causes implies the adoption of that theory according to which each species of plants is originally produced in one spot only, from which it is gradually propagated. Whether this be the only, or the most probable opinion that can be held, it is not my intention to inquire : it may however be stated as not unfavorable to it, that, of the Dicotyledonous plants of the lists, a considerable number have the embryo of the seed highly developed, and at the same time well protected by the texture of its integuments.
This is the case in Malvaceae, Convolvulacese, and parti- cularly in Leguminosge, Avhich is also the most numerous family in the lists, and in several of whose species, as Gici- land'ina Bonchic, and Abrus precatorius, the two conditions of development and protection of the embryo coexist in so remarkable a degree, that I have no doubt the seeds of these plants would retain their vitality for a great length of time either in the currents of the ocean, or in the digestive organs of birds and other animals; the only means apparently by which their transportation from one continent to another can be effected: and it is deserving of notice that these seem to be the two most general plants on the shores of all equinoctial countries.
The Dicotyledonous plants in the lists which belong to other families have the embryo of the seed apparently less
- Sir Joseph Banks informs me, that lie received some years ago the
drawing of a plant, which his correspondent assured him was raised from a seed found on the west coast of Ireland, and that the plant was indisputably Gallandlna Bonduc. Linnaeus also seems to have been acquainted with other instances of germination having taken place in seeds thrown on shore on the coast of Korway. Vide Cohmue Flanlamni, p. 3, in Amoca. Acad, vol, 8.
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