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 Leguminosse, which is also the most numerous 

 family in the lists, and in several of whose species, as Gui- 

 landina Bonduc, and Jbrus 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 Eanks informs me, that he 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 

 Ouilaniina 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 Norway, Vid^ Colonice Plantarum, p. 3, in Amcsn. Acad. vol. 8. 



