1858.] NATURALIZED PLANTS OF GREAT BRITAIN. 451 



•whether the species is still spreading (like Veronica Buxbaumii 

 with us) ; whether it is an annual that produces numerous small 

 seeds likely to spring up readily in tillage ; whether it is a com- 

 mon weed elsewhere, a hardy and encroaching plant ; whether 

 the structure of its seeds offers any unusual facility for transport 

 hy means of hooks, spines, pappus, or glutinous secretion. Above 

 all, it is essential to observe by how great an interval a plant is re- 

 moved from the principal habitation of its own species or genus. 



De CandoUe divides* the plants of a country into cultivated 

 and spontaneous. 



The cultivated comprise two sections. 



1. Those cultivated purposely. 



2. Those cultivated unintentionally ; tillage- weeds, corres- 

 ponding pretty rxcarly with the ^^agrestal colonists" of the 'Cybele 

 Britannica,^ but they include also several (such as Linaria minor) 

 that are termed " agrestal," or even " glareal" natives, as well as a 

 few "aliens." 



In the subdivision of spontaneous species a more elaborate plan 

 is followed by placing them under five heads. 



1. Adventitious : aliens that are not well established. 



2. Naturalized; species thoroughly established and acclima- 

 tized, but of whose foreign origin there is no doubt. 



3. Species perfectly established, but respecting which the pro- 

 habilities are in favour of a foreign origin ; these are by De Can- 

 doUe included with the preceding under one term of naturalized. 



4. Species to whose indigenous origin but slight suspicion is 

 attached. 



5. Indigenous species. 



There are 83 species enumerated as naturalized in Great 

 Britain, they are distributed into the following sections. 



Ten are from North America, and owe their introduction to 

 garden culture or to accidental conveyance with merchandise or 

 in ballast. 



Senebiera didt/ma, L. C, B., H. & A.f Oxalis cornictdata, B., H. & A. 

 Impatiens fiilTa. CEnothera biennis. 



* Any one who feels desii-ous of adopting the distinctions here proposed might 

 employ a double dagger J for the cultivated unintentionally, the brackets [ ] for 

 adventitious species, the asterisk * for the two classes of naturalized plants, re- 

 serving the simple dagger f for cases of sUght suspicion, as in Babington's ' Manual.' 



+ The letters following the species printed in italics are intended to show which 



