45 



number of species left. — The genus Aesculus L. contains the sections Eu-Aesculus, Pavia (Poir.), 

 Macrothyrsus (Spach) and Calothyrsus (Spach), the last three of which were regarded as distinct 

 genera by their respective authors. In the event of these genera being retained the name Aesculus 

 must be kept for the species Aesculus Hippocastanum L. as this is undoubtedly the type of the genus 

 founded by Linnaeus {Sp. pi. ed. 1, 344), as is seen by a comparison with Linnaeus, Hort. Cliff. 

 142, and early editions of the Gen. pi. (ed. 1, 310; ed. 2, 367); Toumefort's name Hippocastanum 

 must not be used as was done by Gaertner (Fruct. ii. 135). 



Art. 46. When two or more groups of the same nature are united, the 

 name of the oldest is retained. If the names are of the same date, the author 

 chooses, and his choice cannot be modified by subsequent authors. 



Examples. — Hooker f. and Thomson {Fl. Ind. 67 [1855]) united the genera Wbrmia 

 Rottb. and Capellia Bl.; they gave the name Wormia to the genus thus formed because the last 

 name dates from 1783 while Capellia dates from 1825. — In case of union of the two genera 

 Cardamine and Dentaria, which were founded at the same time by Linnaeus (Sp. pi. ed. 1, 653 

 and 654 [1753]; Gen. PI. ed. 5, n. 726, 727) the collective genus must be called Cardamine because 

 that name was chosen by Crantz (Class. Crucif., 126 [1769], who was the first to suggest the 

 union. — H. Hallier (in Engl. Bot. Jahrb. XVIII, 123) united the three species of Ipomoea, /. verticillata 

 Forsk. (1775), /. rumicifolia Choisy (1834) and /. Perrottetii Ç\i(m^ (1845); the species is still called 

 /. verticillata Forsk. as Forskal's name is the earliest. — Swartz (Prodr. 16) described two species 

 of Piper, P. glabellum and P. scandens which he subsequently (Fl. Ind. Occ. i. 68) regarded as con- 

 specific, choosing the name P. glabellum'.^ this name therefore and not P. scandens must be used for 

 the combination. 



Biecommendations. 



XXVI. Authors who have to choose between two generic names should note the following 

 recommendations : 



1. Of two names of the same date to prefer the one which was first accompanied by the 

 description of a species. 



2. Of two names of the same date, both accompanied by descriptions of species, to prefer 

 the one, which, when the author made his choice, included the larger number of species. 



3. In cases of equality from these various points of view to prefer the more correct and 

 appropriate name. 



XXVtI. When several genera are united as subgenera or sections under one generic 

 name, that subdivision which was first distinguished or described may retain its name (ex.: Anar- 

 ihinum sect. Anarrhinum\ Hemigenia sect. Hemigenia), or be preceded by a prefix (Anthriscus sect. 

 Eu-Anthriscus) or followed by a suffix (Stachys sect. Stachyotypus). These prefixes or suffixes lapse 

 when the subdivisions are raised to generic rank. 



XXVm. When several species are united as subspecies or varieties under a collective 

 name, that subdivision which was first distinguished or described may retain its name (ex.: Saxifraga 

 aspera subsp. aspera) or bear a prefix (Alchemilla alpina subsp. eu-alpina) or be designated by some 

 customary title (normalis, genuinus, typictis, originarius, verus, veridictis etc.). These prefixes or 

 terms lapse when the subdivisions are raised to specific rank. 



Art 47. When a species or subdivision of a species is divided into two 

 or more groups of the same nature, if one of the two forms was distinguished or 

 described earlier than the other, the name is retained for that form. 



Examples. — Genista horrida DC. Fl. Franc. IV. 500 was divided by Spach (in Ann. Sei. 

 Nat. ser. 3, II., 253 [1844]) into three species: G. horrida DC, G. Boissieri Spach and G. Webbit 

 Spach; the name G. horrida was rightly kept for the earliest described form, that described and 



