480 APPENDIX. No. V. 
natives of Egypt; Glinus lotoides of Egypt and Barbary; and Flagellaria in- 
dica, existing on the east coast of New Holland, in as high 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 subsisted 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 occidentalis ; both of 
which may possibly have been introduced into America by the Negroes, from 
the west coast of Africa ; the 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 Chrysobalanus 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 acci- 
dentally 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 Desmocheta lappacea, Lavenia erecta, Ageratum conyzoides, Grangea ma- 
deraspatana, Boerhaavia mutabilis, and Hyptis obtusifolia ; or from the minute- 
ness of their seeds, as Schwenckia americana, Scoparia dulcis, Jussiaa 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, 
Scoparia dulcis, and Boerhaavia mutabilis, being also natives of the intratro- 
pical part of New Holland; their transportation to or from which cannot be 
supposed to have been effected in any of the ways suggested. 
The probability, however, of these modes of transportation, 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- 
