PREFACE. vii 



best to retain the old limits of the British Flora. The extra-British dis- 

 tributions I worked out myself for most of the British plants, making 

 large use of Nyman's Sylloge (ed. 2). 



Of the altitudes, I have chosen the highest the species attains, and 

 indicated the region where this is attained ; when no elevation is given, 

 the Species is not known to ascend to 1,000 feet, and may be assumed to 

 be a "low-ground" plant. To the doubtfully indigenous Species I have 

 often added Watson's opinion as to whether they are " aliens," "colo- 

 nists," or " denizens," &c. It may be well to repeat here his definitions 

 of these terms, premising that by " native " is meant that the Species 

 has not been introduced by human agency : * 



"A denizen is a Species suspected to have been introduced by man, and 

 which maintains its habitat. A colonist is one found only in ground 

 adapted by man for its growth and continuous maintenance. An alien has 

 presumably been introduced by human agency." 



The estimates of the numbers of Genera in the Orders, and of Species 

 in the Genera, are taken from the Genera Plantarum ; they serve to indi- 

 cate to the student the relative extent of these groups. The indications 

 of their affinities and properties are necessarily extremely brief. The ety- 

 mologies of the generic names I have endeavoured to reduce to really 

 useful limits. Only such English names as are pretty well known are 

 given, and for these I have in many cases been guided by Dr. Alexander 

 Prior's Popular Names of British Plants, a very good book. 



In the First and Second Editions I recorded my obligations to Professor 

 Oliver, Mr. Baker, Professor Dickson, Mr. G. Griffiths, and the Rev. E. J. 

 Linton, for valuable observations and suggestions ; to Mr. Baker especially 

 for aid in classifying the critical forms of Eulus, Rosa, and Hieracium. 



In this, the Third Edition, I have introduced many improvements in the 

 classification and characters of the Orders, Genera, and Tribes, adopted in 



* The vagueness of these definitions is unavoidable ; and their correct application 

 in many cases is exceedingly difficult. Few who have not gone into the^subject have 

 an idea of how many plants would disappear from our Flora were the soil left undis- 

 turbed by man and the lower animals which he rears. I think it probable that both 

 the Shepherd' s-Purse and the common form of the Dandelion would be amongst the 

 lirst to be suppressed. 



