CHAPTER 1 

 INTRODUCTION 



Nomenclature is an inseparable and necessary part of the sci- 

 ence and art of systematic botany. On a factual basis, such as 

 the distinctive morphology, samples of a plant population are 

 classified as a distinct unit, now called a taxon. On evaluation 

 of its resemblances to, and differences from, other taxa, the 

 botanist decides upon its taxonomy, that is, the placement of 

 the taxon into the general system of classification. When this 

 placement is determined, then the correct scientific name, ac- 

 cording to plant nomenclature, must be found. The existing 

 names must be judged as to whether or not they are effectively 

 published, validly published, and with priority. If no available 

 name exists, a new one must be formed. These two steps in the 

 establishment of a taxon are, respectively, taxonomic and no- 

 menclatural. Systematic work is correctly and fully done only 

 when both of these steps are properly carried out. 



Though they have had various and even identical definitions 

 in botanical texts and dictionaries, the following botanical terms 

 are used in this text as here defined: 



Systematic botany or systematics embraces the whole field of 

 systematic work, including the placing of an individual plant into 

 a category of classification or taxon, the assignment of the taxon 

 into the system of orderly arrangement or phylogeny, and the 

 selection of a scientific name. This is divisible into the two 

 following parts: 



Taxonomy deals with the placement of a plant into its smallest 

 taxon, and that taxon into the hierarchy of larger ones in the 

 system. All such modern systems are phylogenetic in character. 



Nomenclature deals with the selection of the correct scientific 

 name for a plant when placed in a particular taxon, in conformity 

 with the legal requirements, that is, with the articles and rec- 



