THE TYPE CONCEPT IN SYSTEMATIC BOTANY^ 
A. S. Hitchcock 
(Received for publication January 8, 192 1) 
The binomial system of nomenclature has been an important factor 
in the development of taxonomy. The increase in the number of known 
species since the time of Linnaeus has been many fold; because of care- 
lessness and ignorance the number of names applied to the species of plants 
has been much greater than the number of species ; the increase in our knowl- 
edge of genetic relationships and the diversity of opinions among botanists 
concerning generic limitations have still further increased the synonymy. 
The confusion arising from these causes soon emphasized the need of a code 
of nomenclature by which the naming of plants might be regulated. Many 
codes have been proposed, but only two have received the support of inter- 
national conferences: the Paris Code of 1867, and the Vienna Code of 1905. 
I have pointed out in another place (Science n. ser. 30: 597. 1909) 
that absolute stability in nomenclature is unattainable so long as botany is a 
growing science. The limits of genera will vary according to the knowledge 
and the opinions of individual workers, and the names of the plants as 
they are assigned to this or that genus will change in a corresponding degree. 
A universal code cannot bring about a permanent nomenclature, but it 
enables botanists to apply names according to definite rules, and this is 
all that we may expect of any code. 
The two codes mentioned have been a great help in stabilizing nomen- 
clature. Experience has shown, however, that they lack definiteness in 
directing the application of names, especially of generic names. In the 
early days of taxonomy a name was applied to a concept rather than to an 
entity. A generic name was based upon all the known species of the genus ; 
a specific name was based upon all the known specimens of the species. 
When a genus was divided the original name was retained for one of the 
parts, usually the larger part, or was sometimes discarded altogether. 
The Vienna Code introduced many reforms, but the procedure for applying 
names when a genus or species was divided was still vague and uncertain 
in its application. 
About 30 years ago a new system began to receive serious attention 
among American botanists, the system of applying names by means of 
types. It is not my purpose here to give a history of this idea, but rather 
to point out some of the advantages of the system. The type concept lies 
^ Read before the Systematic Section of the Botanical Society of America at Chicago, 
December 29, 1920. 
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