AN ACCOUNT OF THE GENUS ARGEMONE. 327 



even more erroneous than that applied to the species by Tournefort 

 and Linnaeus ; numerous as the specimens of yellow-flowered Arge- 

 mone from Ecuador, Peru, and Chili are, they all prove to be only 

 A. ochroleuca. 



When we turn to the Eastern Hemisphere, we are at once 

 struck by the fact that the species has spread much more extensively 

 there than in America. In this it only exemplifies a rule, for 

 which no satisfactory explanation has yet been offered, that weeds 

 of the New World spread more rapidly in the Old, and vice versa.^' 

 Thus it is present in all the Atlantic islands, occurs throughout the 

 whole African seaboard from Senegal to Socotra ; appears in all 

 the islands spoken of as Mascarene ; and is widely diffused through- 

 out South-eastern Asia. 



Tiie early figures of the species are of unequal value, but it is 

 worth noting that all of them unmistakably indicate the true A. 

 mexicana of the Antilles, except the plate in Hernandez, which, 

 though a very poor one, represents a plant with the habit of 

 A. ochroleuca, and not of ^-1. mexicana. J. Bauhin's figure is good 

 and unmistakable ; Miller's is not so good ; Lamarck's is excellent, 

 and represents exactly the plant as represented in Tournefort' s, 

 Le Vaillant's, Cliffort's, Linnteus's, and his own herbaria. It is 

 interesting to find from Lamarck's herbarium that the specimen 

 figured did not come from America, but from the Isle de France, 

 where it was collected by Commerson ! Curtis's figure in the Bot. 

 Mag. is excellent also. 



It is curious to note that while the distribution oi A. mexicana 

 has been zonal, that of A. ochroleuca has been meridional. Instead 

 of spreading eastward to Africa and Asia, like the typical plant, A. 

 ochroleuca. has spread southward along the countries that border the 

 Pacific from Ecuador to Chili, spreading eastward, however, through 

 Bolivia and Argentina to Paraguay and Uruguay. Thus at Monte 

 Video, on the seashore the two forms have been found growing 

 together ; this is the only locality from which both have been 

 reported ; here A. mexicana, extending southward along the 

 Brazipan seaboard, has come into touch with A. ochroleuca, 

 spreading eastward across the Pampas. That A. ochroleuca is 

 no more than an escape from gardens to the east of the Andes 

 is pretty clearly indicated by the notes attached to the Argentine 

 specimens of Hieronymus n. 199, and by the remark, ''sponte 

 crescit, Paraguay, et in omnibus vie. missionarum," attached by 

 Bonplaud to the specimens collected by him in Corrientes. It is 

 not improbable that we have in this remark a clue to the manner 

 in which it has been spread throughout South America, and that 

 it was introduced from Mexico into Ecuador, Peru, and Chili by 

 Spanish missionary priests. 



* The extraordinary diffusion in Tropical Asia! of the American species 

 Tridax procumbens, Mimosa piidica, Ageratum conyzoides, and especially Scojnvia 

 dulci.i, may be selected from among several scores of instances as striking 

 examples of this lohenomenon ; on the other hand, the diffusion, in the pro- 

 portions of a plague, of certain European species, not particularly unmanage- 

 able in their native country, in the Pampas of S. America, illustrates well the 

 same rule. 



