COMJ'AKATIVK VIKW. lO?
existing on the cast coast of New Holland, in as high a hititude as 32^ 8.
4th. It may perhaps be suggested with respect to these lists, that they contain, or even chiefly consist of, plants that during the constant intercourse which has now sub- sisted for upwards of three centuries between Africa, America, and India, may have, either from design or accidentally, been carried from one of these regions to another, and therefore are to be regarded as truly natives of that continent only from which they originally proceeded.
It appears to me, however, that there is no plant included in any of the hsts which can w^ell be sup[)osed to have been purposely carried from one continent to another, unless perhaps Chr^sobalanus Icaco, and Cassia occldentalis ; both of which may possibly have been introduced into America by the Negroes, from the west coast of Africa ; the former as an eatable fnut, the latter as an article of medicine. It seems at least more likely that they should have travelled in tliis than in the opposite direction. But I confess the mode of introduction now stated, does not appear to me very probable, even with respect to these two plants ; both of them being very general in Africa, as well as ill America ; though Crysobalanus Icaco is considered of but little value as a fruit in either continent ; and for Cassia occiden talis, which exists also in India, another mode of conveyance nuist likewise be sought.
Several species in the lists, however, may be supposed to have been accidentally carried, from adhering to, or being mixed with, articles of food or commerce ; either from the nature of the surface of their pericarpial covering, as l)es- mochaeta lappacea, Lavenia erecta, Ageratum conyzoides, Grangea maderaspatana, Boerhaavia mutabilis, and llyptis obtusifolia ; or from the minuteness of their seeds, as Schwenckia araericana, Scoparia dulcis, Jussiaea erecta, and Sphenoclea zeylanica. That the plants here enumerated have actually been carried in the manner now stated is, however, entirely conjectural, and the supposition is by no means necessary ; several of them, as Lavenia erecta, Sco- paria dulcis, and Boerhaavia uuitabilis, being also natives of
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