REHDER: CONCEPT OF TYPE 7 



1846 has priority over R. macrosepalum Maxim, of 1870 and represents the 

 nomenclatural type of the group including R. macrosepalum. There are many 

 cases, particularly in double-flowered forms, as Spiraea pmnifolia Sieb. & Zucc, 

 Rosa Roxburghii Tratt, R. xanthina Lindl. and some other species of Rosa, 

 in which the double-flowered form is the nomenclatural type, while the bio- 

 logical type was described later and, if distinguished by a name, must be treated 

 as a variety or form. In such cases, it is clear which form represents the nomen- 

 clatural and which the biological type, but in species with geographical or 

 ecological variations opinions may differ as to which is to be considered the 

 phylogenetic type, and if each author were allowed to express his opinion by 

 proposing changes in nomenclature, confusion and instability of names would 

 follow\ An author is always. free to express his opinion but has no right to 

 change names or combinations of names which are in accordance with the rules 

 of nomenclature. 



Arnold Arboretum, Harvard University 

 Jamaica Plain, Massachusetts 



