98 USE OF THE FLORA [CH. VI 
the study of the Flora. I have dealt with this section of 
the subject less in detail, because our best Floras give so 
much information that it seemed undesirable to do more 
than attempt to guide the reader in the recognition of 
the genera and principal species by means of external 
features easily observed by anyone with a little care. 
The detailed and critical examination of species, varieties 
and rare forms should always be done with reference to a 
complete Flora. 
