1907] On the Vienna Rules of Nomenclature 33 
of 3 to 5 per cent. of generic names and between 10 and 20 per cent. of 
specific names. Persons judging of this matter are specially urged to 
make careful distinction between changes caused by the new rules 
on the one hand and the host of alterations on the other which are 
rendered necessary by new light upon plant affinities, the limitation 
of species, division of confused genera, etc.— alterations which are 
botanical rather than nomenclatorial in their nature. 
International rules for Botanical Nomenclature chiefly of 
Vascular Plants, 
Chapter I. General considerations and leading principles. 
Art. 1. Natural history can make rio progress without a regular 
system of nomenclature, which is recognized and used by the great 
majority of naturalists in all countries. 
Art. 2. The prescriptions which govern the exact system of botani- 
cal nomenclature are divided into principles, rules and recommenda- 
tions. ‘The principles (art. 1-9, 10-14 and 15-18) are the foundation 
of the rules and recommendations. The rules (art. 10-58), destined 
to put in order the nomenclature which the past has bequeathed to 
us, and to form the basis for the future, are always retroactive: 
names or forms of nomenclature which are contrary to a rule cannot 
be maintained. Recommendations bear on secondary points, their 
object being to ensure for the future a greater uniformity and clear- 
ness in nomenclature: names or forms of nomenclature contrary to a 
recommendation are not a model to copy, but cannot be rejected. 
Art. 3. The rules of nomenclature should neither be arbitrary 
nor imposed by authority. They must be simple and founded on 
considerations clear and forcible enough for everyone to comprehend 
and be disposed to accept. 
Art. 4. The essential points in nomenclature are: 1. to aim at 
fixity of names; 2. to avoid or to reject the use of forms and names 
which may cause error or ambiguity or throw science into confusion. 
Next in importance is the avoidance of all useless creation of names. 
Other considerations, such as absolute grammatical correctness, 
regularity or euphony of names, more or less prevailing custom, 
El 
