50 



ßidered as this combination is contrary to art. 51,1° of the Rules. — Peucedanum Silaus L. (1753) 

 when placed in the genus Silaus must be called Silaus ßavescens Bernh. (1800) ; the earlier synonym 

 Seseli selinoides Jacq. (1762) cannot be considered as this combination is contrary to art. 48 of the 

 Rules. — Polypodium montanum Vogl. (1781) non Lamk (1778) = P. Oreopteris Ehrh. ex Willd. 

 (1789), when placed in the genus Dryopteris must be called D. Oreopteris Max. ; the earlier synonym 

 Polypodium montanum Vogl. cannot be considered as this combination is contrary to the Rules 

 art. 51, 2". It is true that P. montanum Lamk has been transferred later to the genus Cystopteris 

 [C montana (Lamk) Desv.] but the genus Cystopteris dates only from the year 1806; Ehrhart could 

 therefore neither forsee nor take account of it. — See also the examples cited under articles 51 and 53. 

 Art. 57. The original spelling of a name must be retained, except in case 

 of a typographic or orthographic error. When the difference between two names, 

 especially two generic names, lies in the termination, 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 affects the first syllable, and above all the first letter of a name. 



XXXI. Many names differ by a single letter without risk of confusion (ex. Durvillea and 

 Urvilled). 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 Pkuropetalum in Or- 

 chidaceae) only one, the older, of the names should be kept, in accordance with article 51, 4*'. 



Chapter IV. Modification of the rules of botanical nomenclature. 



Art. 58. The rules of botanical nomenclature can only be modified by com 

 petent persons at an international Congress convened for the express purpose. 



Appendix. Various recommendations. 



XXXH. 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, knots, miles etc. are ex- 

 pressions which should disappear from scientific language. 



XXXV. Very minute dimensions are reckoned in ^ (micromillimetres, microns, or thou- 

 sandths 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. 



XXXVI. Authors are asked to indicate clearly and precisely the scale of the figure» 

 which they publish. 



XXXVII. Temperatures are expressed in degrees of the centigrade thermometer of Celsius. 

 XXXVm. It is of the utmost importance that the original specimens on which are based 



the descriptions of new groups should be preserved. In the case of microscopic Cryptogams, the 

 preparations and original drawings should be preserved; and in the case of fleshy fungi, watercolour 

 sketches and specimens suitably prepared or dried, etc. 



