PKEFACE. 
xi 
the specimen to be the same as (idem). As the descriptions 
and figures are not always similar, and the plants vary, 
identification should consist in citing the description, figure, 
or specimen with which a specimen has been matched. The 
use of a name is only a brief way of referring to some 
description in order to avoid either giving a new one for 
every specimen recorded, or presei-ving every specimen. The 
source whence the name is taken should therefore be indicated 
if the identification is to be definite. If this is done, it 
becomes relatively immaterial which of two or three names 
is used, since the meaning is always discoverable. 
It was difficult to decide what to omit from the Appendix. 
So many of the now accepted varieties were deliberately 
omitted by Babington, although others were unknown to 
him. To bring the work up to date in the matter of 
varieties was impossible Avithin the limits set. The Appendix 
has therefore been limited to the more important revisions of 
genera, to additional species, and to certain cases where 
important information could be easUy assimilated to the 
body of the work. To do otherwise would have involved 
considerable re-writing, whereas the aim of this edition Is to 
keep available for the student a work which still occupies 
a position as yet unfilled by any other manual. 
A. J. WILMOTT. 
Wimuledov, 24th April 1922. 
