COMPAKATIVE VIEW. 167 



existing on the east coast of New Holland, in as hie-h a 

 latitude as 32« S. 



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 lists which can well be supposed to have been 

 purposely carried from one continent to another, unless 

 perhaps Chrysobalanus Icaco, and Cassia occidentaUs ; both 

 of which may possibly have been introduced into America 

 by the Negroes, from the west coast of Africa ; th.e former 

 as an eatable fruit, the latter as an article of medicine. It 

 seems at least more likely that they should have travelled 

 in this 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 in America ; 

 though Crysobalanus Icaco is considered of but little value 

 as a fruit in either continent ; and for Cassia occidentalis, 

 which exists also in India, another mode of conveyance must 

 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 Des- 

 mochseta lappacea, Lavenia erecta, Ageratum conyzoides, 

 Grangea maderaspatana, Boerhaavia mutabilis, and Hyptis 

 obtusifoha; or from the minuteness of their seeds, as 

 Schwenckia araericana, Scoparia dulcis, Jussisea 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 mutabiUs, being also natives of 



