52 DATA FOR DETERMINING 



the part of the author or compiler ; while others are 

 omitted, though really existent, in consequence of the 

 works professing to include an extent of country not 

 actually examined. Thus they mislead as well by the po- 

 sitive as by the negative evidence. 



The general Floras of Britain* must be liable to such 

 errors in a much higher degree ; and a work like the 

 Botanist's Guide cannot at all avoid them. Beyond 

 question, there are many and great errors \ in this latter 

 (as the compilers frequently hint), and Withering 's Ar- 

 rangement is probably more faulty still. Various lists of 

 species may be found in Guide-books to watering 

 places, Histories, and Periodicals ; but frequently on in- 

 competent or unexpressed authority, they are very unsafe 

 guides to the botanist afar off. J 



Besides these published data, I have accumulated, by 

 personal labours, and through the kindness of friends and 

 correspondents, a large stock of additional materials upon 

 which I am inclined to place much reliance, having 

 usually been able to apply to the authority for more 

 explicit information when doubts arose. These materials 

 consist of several lists of species for counties or other 

 districts, numerous stations for the rarer plants, and a 

 large number of specimens. Altogether, it is probable 

 that my library and cabinet now contain more data for a 



* Those which have been used are, the English Flora of Smith, and 

 the Flora Scotica and British Flora of Hooker. Lindley's Synopsis of 

 the British Flora does not embrace the localities of plants, except in 

 very few instances. 



•f In the New Botanist's Guide, before alluded to, I have endea- 

 voured to point out what are likely to be errors ; but it cannot be hoped 

 that I have myself avoided committing or perpetuating the errors in- 

 separable from such compilations. 



{ But such as Don's List of the Rarer Plants of Forfarshire (in 

 Headrick's Agricultural Survey of that county), Neill's Additional 

 Plants of Orkney (Tour), Graham's Botanical Excursions in the 

 Highlands (Edinburgh Philosophical Journal), Winch's Catalogue of 

 Plants in North Wales (Mag. Nat. Hist.), may be looked upon as 

 quite trustworthy. 



