CLASSIFICATION AND NOMENCLATURE. 47 



natural system, which is the ultimatum of scientific classifica- 

 tion. The study of life-histories will continually clear up points 

 of relationship before unknown, and it will not be long before 

 the classification will become fixed and constant. Every real 

 study contributes to this end. 



1 23. Changes of Nomenclature. Exactness of citation 

 is of prime importance, and in later years stability in nomen- 

 clature has been an end constantly sought. Nineteen years ago, 

 when the first edition of this work appeared, the serious study 

 of the higher flora of America was largely confined to a single 

 botanical centre, and that centre followed the practice of Kew, 

 the great royal herbarium of England, in adopting names without 

 particular reference to principles of priority. So long as one 

 centre existed, this system was little questioned. But soon new 

 centres of study of our flora were formed, new workers appeared 

 fresh from fields where the study of plants in life had been 

 added to the study of plants in the herbarium. These workers 

 recognized the fact that in neglecting priority and in following 

 no fixed principles of nomenclature, grave difficulties were con- 

 stantly arising, and confusion followed ; they could not follow a 

 system based on so uncertain and variable a standard as the 

 personal system of nomenclature. European botanists, even 

 Englishmen outside of Kew, recognized the same difficulties. 

 There must be a common starting-point accepted ; there must 

 be some common principles adopted and followed for taking up 

 generic and specific names. During the past ten years the bo- 

 tanical world has quite generally settled down to 1753 as tne 

 starting-point of nomenclature,* and most adopt the principle 

 of priority as fundamental ; t e., each generic group is given its 

 oldest tenable name, and each species bears the original specific 

 name assigned it whether it remains in its original genus or 

 is transferred to some other. Some examples will make this 

 clear if we follow the history of individual species. 



1 24. A simple case that has been involved in a recent 

 change of name is seen in our Eastern lip-fern (Cheilanthes) ; the 



* This is purely arbitrary and has been selected for convenience merely. 

 Genera and species were clearly denned before this time. 



