The human transport of animals across the Northern Atlantic 213 



Lepidium densiflorum Schrad. — Transamerican (but probably introduced in the 

 east). — Europe (generally but often casual), N to N Norway. Also in other conti- 

 nents. 



Matricaria matricarioides Less, {discoidea D.C., suaveolens Pursh., nee L.). — Trans- 

 american, native of NW America & NE Asia. — Europe (generally, since about 1850), 

 N to northernmost Scand. S. America, New Zealand. 



Oenothera biennis L.^ — N. America E of Rocky Mts. — Europe (generally, since 

 1 8th century), N to C Finland. 



Oxalis stricta L. — Transamerican, S to Mexico. — Europe (widely, since before 

 1700), N to C Finland. Also in other continents. 



Veronica peregrina L.i — Transamerican, also C & S America. — W & C Europe 

 (since i8th century), N to Denmark. 



To these should be added some 15-20 species of North American origin, lo- 

 cally and mostly only temporarily established, especially on the British Islands. 

 — On Ranunculus cymbalaria Pursh., vide below (p. 244). 



This is a poor representation, indeed! It should also be observed that several 

 of the above plants are late arrivals, apparently introduced after modern steam 

 trade had commenced. 



Turning back to animals, there is only one ecological group in which North 

 American species unintentionally introduced into Europe are far more numerous 

 than those transported in the opposite direction: the hothouse animals, more or 

 less unable to establish themselves out of doors. 



European hothouse species of North^ American origin. 



A. Terrestrial animals. 



Formicidae Helicodiscus parallelus Say 



/-, . , 7- 7 , c Opeas pumilum PfeiflF. 



Lrematogaster lineoiata bay ^ . 



r> ^ • ^ TVT 1 Subulina octona Brug. 



ronera opaciceps Nyl. „ . . , , 



Zonitotdes arbor eus Say^ 



Araneae . 



Lumbricidae 



Eperigone maculata Banks 



Btmastus beddardi Mich. 



Mollusca Eisenia carolinensis Mich. 



Hawaiia minuscula Binn. 



^ Probably originally cultivated in Europe and escaped. 



- Some of these may possibly come from parts of America south of the U.S. A. -Mexican 

 boundary. 



* In part established in outdoor conditions. 



