BOTANICAL NOMENCLATURE 83 



divisional name. They should either repeat that epithet or use one of the customary- 

 epithets, typicus, genuinus, originarvus, etc. E. g. Andropngon caricosus subsp. 

 mollissimus var. mollissim'us Hackol; Arthraxon ciliaris Bcauv. subsp. Langsdorfii 

 var. genuinus Hackel. 



XIX. Botanists proposing new epithets for subdivisions of species should avoid 

 such as have been used previously in the same genus, whether for species or for 

 subdivisions of other species. 



§ 6. Names of Hybrids and Half-hreeds. 

 Art. 31. Hybrids or putative hybrids between species of the same 

 genus are designated by a formula and, whenever it seems useful or 

 necessary, by a name. 



(1) Sexual hybrids. — The formula consists of the names or specific 

 epithets of the two parents in alphabetical order and connected by the 

 sign X. When the hybrid is of known experimental origin the fonnula 

 may be made more precise by the addition of the signs 9 $ , the name 

 of the female (seed-bearing) parent being placed first. 



The name, which is subject to the same rules as names of species, is 

 distinguished from the latter by the sign x before the name : e. g. 

 X Salix capreola {Salix anrita x caprea) . 



(2) Asexual hybrids (graft hybrids, chinueras, etc.). — The formula 

 consists of the names of the two parents in ali)habetical order connected 

 by the sign +. The name has a "specific" epithet different from that 

 of the corresponding sexual hj'brid (if any), and is preceded by the 

 sign +: e. g. + Solanum tubingense {Solanum nigrum + 8. Lycopersi- 

 cum) . 



Art. 32. Bigeneric hybrids (hybrids between species of two genera) 

 are also designated by a formula and, whenever it seems useful or 

 necessaiy, by a name. 



The formula consists of the names of the two parents connected by 

 a sign, as in Art. 31. 



The name consists of a new "generic" name usually formed by a 

 combination of the names of the parent genera, and a "specific" 

 epithet. All hybrids (whether sexual or asexual) between the same 

 two genera bear the same "generic" name. 



(1) Sexual hybrids. — In the formula the connecting sign x is used. 

 The name is preceded by the sign x : e. g. x Odoniioda Boltonii (Coch- 

 lioda Noezlianax Odontoglossum Vuylstekeae) . 



(2) Asexual hybrids. — In the formula the connecting sign + is used. 

 The name is preceded by the sign +. The "specific" epithet is differ- 

 ent from that of the corresponding sexual hybrid (if any) between the 

 same species. E. g. + Laburnocytisus Adami {Laburnum anagyroides 

 +Cytisus purpurens) . 



Art. 33. Ternar.y hybrids, or those of a higher order, are designated, 

 like ordinary hybrids, by a formula and, whenever it seems useful or 

 necessary, bj^ a name. Such as are trigeneric or polygeneric are given 

 new "generic" names usually formed by a combination of the names 

 of the parent genera. 



Recommendation XX. Half-breeds, or putative half-breeds, may be designated 

 by a name and a formula. Names of half-breeds are intercalated among the sub- 

 divisions of a species, and are preceded by the sign x. In tlie formula the names 

 of the parents are in alphabetical order. When the half-breed is of known experi- 

 mental origin the formula may be made more precise by the addition of the signs 

 9 $, the name of the female (seed-bearing) parent being placed first. 



