52 Rhodora Marcu 
between two names, especially two generic names, lies in the termi- 
nation, these names are to be regarded as distinct even though differing 
by one letter only. 
Examples: Rubia and Rubus, Monochaete and Monochaetum, Peponia and 
Peponium, Iria and Iris. 
Recommendations. 
XXX. The liberty of making orthographic corrections must be used with 
reserve, especially if the change effects the first syllable, and above all the 
first letter of a name. 
. Many names differ by a single letter without risk of confusion 
(ex. Durvillea and Urvillea). In cases where a close approach to identity 
is a source of error (ex. Astrostemma and Asterostemma in one and the same 
family, Asclepiadaceae, Pleuripetalum and Pleuropetalum in - Orchidaceae) 
only one, the older, of the names should be kept, in accordance with article 
51, 4°. 
Chapter IV. Modifications of the rules of botanical nomenclature. 
Art. 58. The rules of botanical nomenclature can only be modified 
by competent persons at an international Congress convened for the 
express purpose. 
Appendix. Various Recommendations. 
XXXII. Botanists should use in modern languages latin scientific names. 
or those immediately derived from them, preferably to names of another 
kind or origin. They should avoid the use of the latter unless these are very 
clear and in common use. 
XXXIII. Every friend of Science should oppose the introduction into a 
modern language of names of plants which are not already there, unless they 
are derived from latin botanical names by means of some slight alteration. 
XXXIV. The metric system only is used in botany for reckoning weights 
and measures. The foot, inch, line, pound, ounce etc. should be rigorously 
excluded from scientific language. 
Altitude, depth, rapidity etc. are measured in metres. Fathoms, knóts, 
miles etc. are expressions which should disappear from scientific language. 
XXXV. Very minute dimensions are reckoned in p (micromillimetres, 
microns, or thousandths of a millimetre) and not in fractions of a millimetre 
or line, etc.; fractions encumbered with ciphers and commas are more likely 
to give rise to mistakes. 
. Authors are asked to indicate clearly and precisely the scale 
of the figures which they publish. 
XXXVII. Temperatures are expressed in degrees of the centigrade- 
thermometer of Celsius. . 
