Vm PREFACE. 



Even thus, however, the difficulties he has had to en- 

 counter have been greater than would be easily imagined 

 by any one who had not actually undertaken a task of the 

 same kind. Nothing, he feels, could justify the conclu- 

 sions at which he has arrived, respecting the union of 

 many Genera and Species, but the power of examining 

 the almost countless specimens, preserved either in his 

 own peculiarly rich herbarium, or in the many others, as 

 well public as private, to which he has been allowed ac- 

 cess. The opportunities, thus afforded, of comparing the 

 same species, in its varied forms, and from different, in- 

 deed often from widely severed, localities, have proved of 

 the utmost utility. They have enabled him to arrive at 

 results, to which no other means of investigation could 

 have led. These results, he is aware, are but too likely to 

 startle other students of the same tribe of plants ; and in- 

 deed he is not ignorant that the so frequent junction of 

 supposed distinct species, in the following pages, has al- 

 ready called forth expressions of surprize from the pens of 

 able botanists. He needs, however, scarcely state, that such 

 an amalgamation of supposed genera and species has never 

 been made without the most careful investigation ; and he 

 must be allowed to add, that the further this investigation 

 has proceeded, the more is he convinced that the system 

 of curtailment ought to be, and will be, carried to a still 

 greater length. There is, perhaps, no family of plants 

 where more false species have been made, than among the 



