Xii PEEFACE. 



alterave vice tantum obviis ; parum vero curans titrum planta 

 ceterum auctorum vel primitus introducta videatur ; ad hanc 

 classem ublque longe plures pertinent quam vidgo fingitur et ple- 

 rumque de liac re certum quodclam statiiere impossibile est." 

 Fries, Corpus Flor. Provin. Suec. i. Fl. Scan. p. xiii. 



In a local Flora like the present, the insertion of a few spe- 

 cies of confessedly extraneous origin, provided they are 

 honestly indicated as such to obviate the propagation of error, 

 can be productive of no detriment to botanical science. Such 

 subspontaneous species have bona fide earned a title to citizen- 

 ship, by taking possession of the soil ; yet their claim as deni- 

 zens should be admitted with judgment, and only allowed after 

 a tenure of some duration. As a further precaution, it is 

 advisable to mark such interlopers with the brand of Italics, 

 the attachment of an asterisk or other sign of exception, or to 

 allot them a separate place in an appendix. The second of 

 these methods I have adopted, as being simple and most in 

 conformity with the general practice of other writers, and 

 because the amount of such certainly introduced species is too 

 inconsiderable to be worth while throwing them into a page by 

 themselves. 



I am of opinion that the best and safest criterion for resolv- 

 ing doubtful claims to enrolment is to be sought for by refe- 

 rence to the geographical distribution of the species under con- 

 sideration. The more extended study of this important branch 

 of botanical science would, I am persuaded, go far in removing 

 many of those scruples that are raised against the admission of 

 no small number of our vegetable productions into the aborigi- 

 nal lists. Proceeding on this principle, I have briefly noticed 

 the geographical range of every plant on which such doubt has 

 been or may be cast, referring to those natural limits as pre- 

 sumptive though not absolute proof in favour of admission, 

 being quite aware that the exceptions to the apparent law of 

 distribution are too numerous to warrant our drawing more 

 than general conclusions therefrom. 



In accordance with the sound principle adopted by the bota- 

 nists of this country in the preparation of general or local 

 Floras, and which our continental brethren would do well in 

 following, every tree, shrub or herb whose sole pretensions to 

 admission rest on the universality of its cultivation, or subser- 



