Notice of a Flora of North America. 283 



arbitrary arrangement of them in separate series. In some sort, 

 these do no doubt exist, but the differences are scarcely more 

 than matters of degree^ and hence, where extensive means of 

 comparison are not within reach of the student, the appreciation 

 of the terms necessarily employed to describe these variations, 

 becomes mere matter of opinion, and therefore open to misappre- 

 hension. These dilRculties, inseparable from the nature of the 

 case, are not within the control of any systematic writers, and 

 we believe that the present arrangement will not disappoint the 

 hopes of the authors, who " trust that most of our indigenous 

 Asters may be satisfactorily identified by the student." * * * 

 We shall only further notice the kindred and very difficult 

 genus Brigeron, which we shall do in the succinct and philo- 

 sophical observations of Drs. Torrey and Gray : 



" It appears to us impossible to effect generic divisions among these 

 plants, by characters derived from the single or double series of rays, 

 or from the simple or double pappus, or by any combination of these. 

 The characters of our sections, or sub-genera, exhibit the diversities 

 which the North American species present in these respects. As a 

 whole, the genus is distinguished from Diplopappus by the very short 

 and obtuse appendages of the style, the nearly simple involucre, and 

 the naked receptacle : the same charactex's also distinguish it from 

 Aster; but the alpigenous Asters almost connect the two genera." 



The genus has been entirely remodelled, and bears ample tes- 

 timony, no less to the science than to the unwearied patience 

 which have been devoted to the subject. We feel justified, in- 

 deed, in extending this encomium, not merely to the last num- 

 ber, but also to the entire work of Drs. Torrey and Gray, so far 

 as it is before the public ; and we trust, for the sake of natural 

 science, more especially that branch of it so much below its just 

 appreciation in our own country, that this most valuable contri- 

 bution towards its elevation, may be carried to completion by the 

 laborious and talented authors. J. C. 



