BOTANICAL NOMENCLATURE 79 



VII. The utmost importance should be given to the preservation of the orginal 

 ("type") material on which the description of a new group is based. In micro- 

 scopic Cryptogams the preparations and original drawings, in fleshy Fungi water- 

 colour drawings and specimens suitably piepared or dried, should be preserved. The 

 original account should state where this material is to be found. 



Section 3. — Limitation of the Principle of Priority: publication, start- 

 ingf-points, conservation of names (Art. 19-22). 



Art. 19. A name of a taxonomic g-ronp has no status under the 

 Rules, and has no claim to recognition by botanists, unless it is validly 

 published (see Section 6, Art. 37). 



Art. 20. Legitimate botanical nomenclature begins for the differ- 

 ent groups of plants at the following dates: — 



{a) Phanerogamae and Pteridophyta, 1753 (Linnaeus, Species Plan- 



tarum, ed. 1). 

 (&) Muscineae, 1801 (Hedwig, Species Mnscorum). 



(c) Sphagnaceae and Hepatieae, 1753 fLinnasus, Species Pkmtarum, 

 ed. 1). 



(d) Lichenes, 1753 (Linnasus, Species Plantarum, ed. 1). 



{e) Fungi: Urediuales, Ustilaginales and Gasteromycetes, 1801 (Per- 

 soon, Synopsis methodica Fungorum) . 



(/) Fungi cfeteri, 1821-32 (Fries, Systema mycologicum) . 



(g) Algae, 1753 (Linnasus, Species Plantarum, ed. 1). 



Exceptions. — Nostocaceae homocysteae, 1892-93 (Gomont, 

 Monographic des Oscillariees in Ann. Sci. Nat. ser. 7, Bot. vi. 

 91; vii, 263). — Nostocaceae heterocysteae, 1886-88 (Bomet et 

 Flahault, Revision des Nostocacees heterocystees in Ann. Sci. 

 Nat. ser. 7, Bot. iii, 323 ; iv, 344; v, 51 ; vii, 177). — Desmidiaceae, 

 1858 CRalis, British Desmidiaceae) . — Oedogoniaceae, 1900 (Hirn, 

 Monographic und Iconographie der Oedogoniaceen in Act. Soc. 

 Sci. Fen7i. xxvii, No. 1). 



{h) Myxomycetes, 1753 (Linnaeus, Species Plantarum, ed. 1). 



The nomenclature of Fossil Plants of all groups begins with the year 

 1820. 



It is agreed to associate generic names which appear in Linnseus's 

 Species Plantarum., ed. 1 (1753) and ed. 2 (1762-63), with the first 

 subsequent descriptions given under those names in Linngeus's Genera 

 Plantarum, ed. 5 (1754) and ed. 6 (1764). 



Art. 21. 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 

 the dates given in Art. 20, the Rules provide a list of names which 

 must be retained as exceptions. These names are by preference those 

 which have come into general use in the fifty years following their 

 publication, or which have been used in monographs and important 

 floristic works up to the year 1890. 



Note 1. — These lists of conserved names will remain permanently open for addi- 

 tions. Any proposal of an additional name must be accompanied by a 

 detailed statement of the cases for and against its conservation. Such 

 proposals must be submitted to the Executive Committee, who will refer 

 them for examination to the Special Committees for the various taxonomic 

 groups. 



