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AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
at the basis of modern botanical nomenclature. The type species of a 
genus or the type specimen of a species is the species or the specimen respec- 
tively that directs or controls the application of the generic or specific 
name. A generic name shall always be so applied as to include its type 
species; a specific name shall always be so applied as to include its type 
specimen. The old concept was that a genus was a group of species having 
a given combination of characters ; a species, similarly, a group of specimens. 
The new or type concept is that, from the nomenclatural standpoint, a 
genus is a group of species allied to the type species, a species a group of 
individuals similar to the type specimen. 
If a genus or species is divided, that part which includes the type species 
or specimen retains the generic or specific name, be this part relatively 
large or small. The American Code^ recognized the type concept as a 
fundamental principle. The Paris and Vienna codes do not refer to this prin- 
ciple. But the idea had made such headway by 1910 that it was recognized 
by the Brussels Congress in a recommendation as a guide for the future 
(an addition to Recommendation XVIII). This reads: 
[Botanists will do well, in publishing, to conform to the following recommendations: 
XVIII . . . ] XVIII his. When one publishes the name of a new group, to indicate 
carefully the subdivision which is considered to be the nomenclatural type of the group; 
the type genus of a family, the type species of a genus, the type variety or the type specimen 
of a species. This precaution avoids the nomenclatural difficulties in the case where, in 
the future, the group in question comes to be divided. (Act. Congr. Internat. Bot. Brux. 
1910 i: 105.) 
It is to be regretted that this recommendation was not made retroactive. 
I feel confident that the retroactive fixation of nomenclatural types is a 
fundamental necessity in stabilizing nomenclature. I feel confident also 
that this aspect of the type concept will appeal more and more strongly to 
the followers of the Vienna Code as its advantages are recognized, especially 
as there is nothing in the concept that is contrary to the principles of that 
code. One must carefully distinguish between the concept itself and the 
rules for its application. The American Code has recognized the principle 
of types and has also formulated rules for type fixation. One may accept 
the principle and reject these particular rules. 
The congress which adopted the Vienna Code appears to have been 
actuated by a desire to formulate rules that should, in a general way, 
preserve the current usage of generic names. I wish to point out to the 
followers of the Vienna Code that this laudable purpose can be accomplished 
with greater definiteness by applying the type concept than by applying 
the vague and uncertain rules adopted by the Vienna Congress. 
The Vienna Code contains the following rule : 
Art. 45. When a genus is divided into two or more genera, the name must be kept and 
given to one of the principal divisions. If the genus contains a section or some other 
2 Formulated in 1907 by a Nomenclature Commission of the Botanical Club of the 
American Association for the Advancement of Science. 
