OF ABTS AND SCIENCES. 163 



XII. 



CONTRIBUTIONS TO NORTH AMERICAN 

 BOTANY. 



By Asa Gray. 



Presented February 8, 1882. 



I. Studies of Aster and Solidago in the Older Herbaria. 



Aster and Solidago in North America, like Hieracium in Europe, 

 are among the larger and are doubtless the most intractable genera of 

 the great order to which they belong. In these two genera, along 

 with much uncertainty in the limitation of the species as they occur 

 in nature, there is an added difficulty growing out of the fact that 

 many of the earlier ones were founded upon cultivated plants, some of 

 which had already been long in the gardens, where they have under- 

 gone such changes that it has not been easy, and in several cases not 

 yet possible, to identify them with wild originals. Late flowering 

 Compositce, and Asters especially, are apt to alter their appearance 

 under cultivation in European gardens. For some the season of 

 growth is not long enough to assure normal and complete develop- 

 ment, and upon many the difference in climate and exposure seems to 

 tell in unusual measure upon the ramification, inflorescence, and mvo- 

 lucral bracts, which afford principal and comparatively stable characters 

 to the species as we find them in their native haunts. I am not very 

 confident of the success of my prolonged endeavors to put these 

 genera into proper order and to fix the nomenclature of the older 

 species ; and in certain groups absolute or practical definition of the 

 species by written characters or descriptions is beyond my powers. 

 But no one has ever seen so many of the type-specimens of the species 

 as I have, nor given more time to the systematic study of these 

 genera. The following notes should therefore be of use. 



It is noticeable that the herbarium of Nees von Esenbeck for Aster 

 is not referred to. / cannot ascertain what has become of it. But 



