258 A TEXT-BOOK OF GRASSES 
CODES OF BOTANICAL NOMENCLATURE 
282. Botanists have recognized the necessity of being 
governed by a definite system in nomenclatorial matters, 
and many have adopted sets of rules or codes. The best 
known of the earlier codes is that adopted at the Inter- 
national Botanical Congress held in Paris in 1867. The 
report was edited by Alphonse de Candolle and the Eng- 
lish translation is entitled ‘‘Laws of Botanical Nomencla- 
ture.” The report should be read by all interested in 
nomenclature. 
283. Vienna code——The most important recent code 
is that adopted by the International Botanical Congress 
held at Vienna in 1905, and entitled, ‘International 
Rules of Botanical Nomenclature.” A few of the princi- 
ples are here excerpted in order to indicate the general 
trend of the rules. 
Botanical nomenclature begins with the “Species Plantarum” 
of Linnzeus (1753) for all vascular plants. (Art. 19.) 
However, to avoid disadvantageous changes in the nomen- 
clature of genera by the strict application of the rules of nomen- 
clature, and especially of the principle of priority in starting from 
1753, the rules provide a list of names which must be retained in 
all cases. The list forms an appendix to the rules [usually referred 
to as “list of nomina conservanda’’]. (Art. 20.) 
No one is authorized to reject, change or modify a name (or 
combination of names) because it is badly chosen, or disagreeable, 
or another is preferable or better known, or because of the existence 
of an earlier homonym which is universally regarded as non-valid, 
or for any other motive either contestible or of little import. 
(Art. 50.) 
When a species is moved from one genus into another, its specific 
epithet must be changed if it is already borne by a valid species of 
that genus. (Art. 53.) 
The list of nomina conservanda referred to under article 20 
includes the following American grass genera: 
