280 Notice of a Flora of North America. 



These are distinguished by characters of greater or less impor- 

 tance, and, in so extremely natural a group, it follows, almost of 

 course, that in some instances they are incapable of any very 

 precise definition. Following the order of our authors, we have 

 one, or possibly two, species of Galatella^ Cass., though appa- 

 rently very rare, and even doubtful natives of the United States. 

 It is remarked, that " Galatella scarcely differs from Linosyris, 

 except by the presence of (white or blue) rays ; and these, ac- 

 cording to Ledebour, are sometimes wanting in G. dracun- 

 culoides : the two genera have also nearly the same geographical 

 range. The sterile rays chiefly distinguish it from Aster ^ ? 

 Orthomeris, (species of Calimeris of authors ;) to which Aster 

 nemoralis, Ait., belongs." The genus tSericocarpus, of Nees, 

 consisting of five species, is retained by Drs. Torrey and Gray, 

 and it forms, no doubt, a natural group, distinguished by habit, 

 the densely silky achenia, &c., but, as both they and Mr. Nuttall 

 remark, so nearly connected with Aster, through A. gracilis, 

 that we should, upon the whole, have preferred seeing these 

 plants reunited to that genus, though, perhaps, the distinctive 

 characters may be a shade more important than those of Biotia 

 and Tripolium, which are both described under different sec- 

 tions of Aster, and from which, we think, they cannot con- 

 veniently be separated. After all, it is a matter of small mo- 

 ment, practically considered, whether the subdivisions recogni- 

 zable in large and very natural genera, be ranked as sections 

 merely, or as independent generic forms ; the sole dilference 

 being the value and importance of the discriminative characters 

 which they respectively present ; and upon these points, which 

 vary materially in different families, the most profound botanists 

 are not unfrequently at issue. But, in such genera as Aster, Sax- 

 ifraga, (Enothera, and some others, in which we cannot but 

 notice the continual recurrence of intermediate forms, connect- 

 ing the subdivisions with each other by characters possessed by 

 them in common, we prefer a combination of the whole, by the 

 larger and more comprehensive generic type, under which, as it 

 appears to us, the sub-genera or sections may be studied with 

 equal, if not greater facility. Under the several subdivisions of 

 the genus Aster, Drs. Torrey and Gray enumerate, in all, one 

 hundred and thirty-one species, of which number eight are new, 

 and described for the first time, whilst nine species, said to have 



