POSTSCEIPT. 



Tlie first volume of this treatise bears on its title-page 

 the date of 1847 ; the present volume will be dated in 

 1859, the year of its completion. The interval is long, 

 and is incompatible with strict uniformity in a work on 

 science, more particularly in one relating to a department 

 of science which is recent in its origin, and which is 

 scarce yet definitely outlined. During the full dozen 

 years of interval, neither phytography nor phyto-geo- 

 graphy have stood still. Nor have the author's own 

 ideas and inspirations been quite unchangeable during 

 the same period. 



Those readers who may seek to understand the C3'bele 

 Britannica, to use it and to judge it, will of course bear 

 in mind that later statements must be taken to qualify 

 earlier statements, where discrepancy may become mani- 

 fest. Even this one concluding volume by itself, apart 

 from the three former volumes, may require some such 

 consideration ; its earlier pages having been in print a 

 full year before the latter pages were written. Circum- 

 stances of no public interest left the author only an 

 option between desultory writing, much interrupted by 

 other calls on his time and thoughts, and indefinite post- 

 ponement of a concluding volume. 



