296 CONCERNING NOMENCLATURE. 
name to a plant, but since he was the first to recognise 
the utility of a binomial system of nomenclature, and 
to establish such a system upon a sound basis, botanists 
have unanimously agreed to begin their nomenclature 
with the publication of his “ Species Plantarum ” in 1753. 
In this work was included every species of plant known 
to Linnaeus and the names he there gave them are the 
ones botanists are supposed to use. One thing, how- 
ever, has conspired to make a large number of changes 
in these names not only permissible but necessary. 
This is the broad view of genera taken by Linnzus. 
He placed all the ferns in a very small number of genera. 
In his genus Polypodinum, for example, were placed species 
that are now found in Cystopteris, Aspidium, Polystichum 
and Phegoptcris. Subsequent study convinced botanists 
that many of these species were distinct enough to be 
placed in separate genera and this was accordingly done, 
the generic name, of course, having to be changed in 
the process. Unfortunately for nomenclature, these 
botanists, working remote from one another, frequently 
made different genera for the same species without 
knowing it. Thus the rusty Woodsia was known to 
Linneeus as Acrostichum Llvense, to Swartz as Polypodium 
Ilvense, to Michaux as Nephrodium rufidulum and to 
Willdenow as Aspidium rufidulum. Since we are sup- 
posed to always use the earliest name, it often becomes 
a nice question to decide which is first. Not only this, 
but different authors sometimes gave the same name to 
different plants unaware that it had been used before, 
Under these circumstances it has become necessary in 
exact science to add the name of the author to each com- 
bination of generic and specific names to show which 
species is meant. 
