PREFACE. 
has been laid down as a rule by some botanists, that no 
plant can be a species whose distinctive characters are not 
as manifest in an herbarium as when it is alive. We are 
told that our business as descriptive botanists is not " to 
determine what is a species," but simply tojdesciibe plants 
so that they may be easily recognized from the dry speci- 
men. The Author cannot agree to this rule. Although he, 
in common with other naturalists, is unable to define what 
is a species, he believes that species exist, and that they may 
often be easUy distinguished amongst living plants, even 
when separated with difficulty from their allies when dried 
specimens only are examined. He also thinks that it is 
our duty as botanists to study the living plants whenever 
it is possible to do so, and to describe from them ; to write 
for the use and instruction of field- rather than cabinet- 
naturahsts — for the advancement of a knowledge of the 
plants rather than for the convenience of possessors of her- 
baria : also, that the differences which we are able to de- 
scribe as distinguishing plants, being taken from their more 
minute organs, is not a proof that they constitute only a 
single species. It seemS to be our business to decide upon 
the probable distinctness of plants before we attempt to 
define them ; to make the species afford the character, not 
the character form the species. 
This volume being intended as a field-book or travelling 
companion for botanists, it is advisable to restrict the space 
allotted to each species as much as ^wssible, and accordingly 
the characters and observations are onh' such as appear to 
be necessary for an accurate discrimination of the plants. 
Synonyms have been almost wholly omitted ; but usually 
one British, and often a foreign figure of each plant is 
(]uoted. Localities are only given for new or rare plants. 
Mr. Watson's New Botan-isfs Guide and his later publica- 
tions made it unnecessary inconveniently to swell the present 
