2132 A TEXTBOOK OF THEORETICAL BOTANY 



Family, every Family to an Order, every Order to a Class and every Class 

 to a Division. 



Article 12. Where necessary these larger groups may be split up into 

 intermediate groups by putting the prefix sub before the name of the group, 

 i.e., sub-Family, sub-Order, etc. 



Article 16. Each group with a given circumscription, position and 

 rank can bear onlv one valid name, the earliest that is in accordance with 

 the Rules of Nomenclature. 



Article 19. The name of a taxonomic group has no status under the 

 Rules and no claim to recognition by botanists unless it is validly published. 



Article 20. Legitimate botanical nomenclature begins for the different 

 groups of plants at the following dates: 



(a) Phanerogamia and Pteridophyta — 1753 (Linnaeus, " Species 



Plantarum ", Ed., i). 

 {h) Musci — 1801 (Hedwig, " Species Muscorum"). 

 (c) Sphagnaceae and Hepaticae — 1753 (Linnaeus, " Species Planta- 



rum ). 

 {d) Lichenes — 1753 (Linnaeus, " Species Plantarum"). 

 {e) Fungi (Uredinales, Ustilaginales, Gasteromycetes) — 1801 (Persoon, 



" Synopsis Methodica Fungorum"). 

 (/) Fungi (other than those above) — 1821-32, Fries (" Systema 



Mycologicum"). 

 {g) Algae — 1753 (Linnaeus, " Species Plantarum "), with the exception 



of the Desmids — 1848 (Ralfs, " British Desmidiaceae"), 



Oedogoniaceae — 1900 (Hirn, " Monog. u. Ikonograph. d. 



Oedogoniaceen ") and certain groups of the Nostocaceae. 

 {li) Myxomycetes — 1753 (Linnaeus, " Species Plantarum "). 



The starting-point of the nomenclature of the Bacteria, Diatomaceae, 

 Characeae and of some other groups, has not yet been decided. The 

 nomenclature of Fossil Plants begins with the year 1820. 



Article 21. To avoid disadvantageous changes in the nomenclature of 

 genera by the strict application of the Rules of Nomenclature and especially 

 of the principle of priority in starting from the dates given in Article 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. Such names 

 are known as Nomina Conservanda. 



Article 23. Names of Families are taken from the name of one of their 

 Genera, or from a synonym, and end in -aceae. Exceptions, i. The 

 following names, sanctioned by long usage, are treated as exceptions to the 

 Rule: Palmae, Gramineae, Cruciferae, Leguminosae, Guttiferae, Umbelli- 

 ferae, Labiatae, Compositae. Botanists are authorized however to use as 

 alternatives the appropriate names ending in -aceae. 2. Those who regard 



