58 BULLETIN UNITED STATES GEOLOGICAL SURVEY. [Tol.VI. 



extra-tropical South America. Oa the Atlantic side there appears to 

 have been only a slight commingling of warm-temjjerate United States 

 plants with the flora of the nearer tropical districts. Thus, the island 

 of Cuba has Pinus Elliottii {Gubensis), Illicium parviflorum, some species 

 of Asimina, all the Nymphwacece of the Atlantic flora, Ascyrum amplexi- 

 caule, &c., our Ampelopsis and Vitis hipinnata, Ilex BaJioon, a Rhexiay 

 Oldenlandia glomerata, Soustonia patens, Fteroccmlon, Andromeda nitida, 

 Cyrilla, Sahbatia gracilis, Mitreola petiolata, Lachnantiies tinctoria, Mayaca, 

 &c. These, the Ampelopsis excepted, are peculiar to the Atlantic coast. 

 Cuba, moreover, has a species of Kalmia ! 



But more speculative interest arises from the consideration of the 

 North American types, and in many cases the actual species, which re- 

 appear beyond the tropic in South America, on the western and not 

 rarely on the eastern side of that continent. There are a number of 

 X)lants indigenous to Chili, the presence of which in California — where 

 they are seemingly no less indigenous — may be accounted for by the 

 immigration of men and cattle. This may have been the case with 

 Senebiera, Pentaccena, Accena trifida, Plectritis {BetJ^ea) samolifolia, Bow- 

 lesia lobata, Amblyopappus pusillus, Pectocarya, Lastarricm, and the like. 

 For Erodium ciciitarium, Medicago dentieulata, Melilotus parviflora, Oli- 

 gomeris subulata, and Avena fatua, which are now equally at home in 

 California, probably arrived by that route rather than direct from Eu- 

 rope. But we cannot in this way explain the presence in the two tem- 

 perate zones of plants such as the following, which w^e assume to be 

 I^orth American species or types dispersed into South America. Some 

 few of them might with equal likelihood be viewed as Chilian types 

 with abnormal northern dispersion. We enumerate only such as come 

 to view without i^articular search, and exclusive of those which may 

 have been dispersed under man's unconscious agency. Identical species 

 in italics : 



Anemone decapetala. Trifoliiim microdorit 



Anemone multifida. HosacJcia subpinnata. 



Myosurus aristatus. Lathyrus maritimus. 



Sisymbrium canescens. Hoflmanseggia. 



Vesicaria, said to be arctica. Prosopis (Algarobia) juliflora. 



Malvastrum of Forth American Prosopis (Strombocarpa) sp. aft'. 



tyj)e. Fragaria Chilensis. 



Sphseralcea of North American type. Lepuropetalon spathulatum (Atlantic 

 Modiola multifida (Atlantic). and Chilian). 



Sida (Pseu do -Malvastrum) sulphu- Gayophytum sp. 



rea. CEnothera sp. aff. 



Elatine Americana. CEnothera dentata. 



Larrea. CEnothera cheiranthifoUa. 



Ehus § Lithrsea. Boisduvalia sp. 



Lupinus microcarpus. Godetia sp. 



TrifoUum Macriei. Mentzelia sp. aft". 



