Notice of a Flora of North America. 281 



been founded on native specimens by European botanists, are 

 unknown to our authors ; and no less than twenty-two species, 

 professedly described originally from garden specimens, (some of 

 them of doubtful origin,) have not been identified with native 

 plants. On this subject, Drs. Torrey and Gray remark : 



" It is well known that many of the enumerated species, both of 

 earlier and later authors, have been described from plants long cultiva- 

 ted in European gardens, where they have doubtless undergone great 

 alterations in appearance ; to say nothing of the strong probability of 

 occasional hybridization. A large and indeed increasing number of 

 these are only known as garden plants ; and it is probable that many 

 will never be identified with their original types ; even supposing them 

 to have been derived in all cases from this country, which is by no 

 means certain. As we have chiefly directed our attention to the indi- 

 genous plants, and have drawn our descriptions from these alone, we 

 have thought it advisable to bring together, at the close of our account 

 of the proper Asters known to us, those species of garden origin 

 which we have not identified with native specimens. A fuller compar- 

 ison than we have been able to institute, will doubtless considerably 

 reduce their number. Those botanists who are most familiar with our 

 Asters, in their native situations, and with the changes produced by 

 difference of soil, exposure, season, iSsc., will not be greatly surprised 

 at numerous reductions of species, which others may think unwar- 

 ranted. We have only to say, that we have seldom ventured upon 

 such reductions, except on the authority of a full suite of specimens 

 which appeared to present absolute transitions. An obvious differ- 

 ence between two or three specimens is often entirely inappreciable in 

 a fuller series, and thus loses its value as a means of distinction ; but 

 the claims of a genuine species are generally confirmed by a large 

 number of specimens. It must, however, be admitted, that in this as 

 in all large and natural genera, several species which we cannot but 

 consider as distinct, (such for instance as A. cordifolius and A sagitti- 

 folius,) do frequently present very puzzling intermediate forms ; and 

 that an apparent transition is not always real. Yet it is better, per- 

 haps, to hazard the occasional reduction of even true species to varie- 

 ties, than to multiply species which we are confessedly unable to de- 

 fine. We may remark in conclusion, that we are the more inclined to 

 act upon our own convictions, on account of the very frequent and 

 wide disagreement even of the highest authorities upon this genus." 



Now, these observations are very just, and will be at once con- 

 firmed by the personal experience of the very few of our bota- 



Vol. xLi, No. 2.— July-Sept. 1641. 3G 



