248 Distinctions between the Linncean Genera 



Art. XIV. On the Distinctions between the Linncean Genera Poten- 

 tilla and Tormentilla, By Charles C. Babington, B.A. 

 F.L.S. &c. 



The genera Potentilla and Tormentilla are allowed by 

 Linne to differ only in number *, and it has long appeared to 

 me that those botanists who consider them as forming parts of 

 one and the same genus conform more exactly to the Linnaean 

 rules f (which are also those of nature) than he did himself. 

 The genera must be admitted to be extremely close in habit, 

 and the only other difference consists in the number of the 

 petals and sepals, Potentilla having 1 sepals and 5 petals, and 

 Tormentilla 8 sepals and 4 petals.} Number alone, there- 

 fore, being depended upon in this instance, the following 

 tables, drawn up from the examination of 2794 specimens of 

 Tormentilla officinalis of Smith, cannot but be interesting. 

 The specimens were gathered, at the latter end of last August* 

 in Needwood Forest, Staffordshire. 



The calyx in the genera now under consideration appears 

 to consist of two whorls of sepals, alternating with each other, 

 of which one (the outer?) has generally much smaller sepals 

 than the other. I have, therefore, in the tables, distinguished 

 them as " large" and " small." The large whorl, which is 

 alternate with the petals, does not appear to vary much in 



* Linne says, under Potentilla, in his Genera Plantarum y ed. of 1767, 

 " Deme unicam quintam partem numero in omnibus partibus fructificationis, 

 et habebis Tormentillam." [Take away from the number of the parts of 

 fructification in Potentilla a fifth part, and you will have the genus Tor- 

 mentilla.] He also says, under Tormentilla, in the same work, " Tormen- 

 tilla solo numero differt a Potentilla, hinc possent ambo genera combinari." 

 [The genus Tormentilla differs from Potentilla in number alone, and hence 

 these two genera may be united.] 



f The rules to which I refer are the following, which he strongly im- 

 presses on all botanical students : — " Scias characterem non constituere 

 genus, sed genus characterem ; characterem fluere e genere, non genus e 

 charactere; characterem non esse, ut genus fiat, sed ut genus noscatur." 

 (Lin. Philosophia Botanica, p. 119.) [You should know that a character 

 does not constitute a genus, but a genus a character ; that a character pro- 

 ceeds from a genus, not a genus from a character ; a character is not 

 formed that a genus may be constituted, but that a genus may be known.] 



% I append the essential generic character, copied from Lin. Systema 

 Natures, ed. 12. p. 350. and 352.: — " Potentilla, cal. 10-fidus, pet. 5; 

 sem. subrotunda, nuda, receptaculo parvo exsucco affixa." [Calyx 10-cleft, 

 petals 5 ; seeds roundish, naked, affixed to a small dry receptacle.] 

 " Tormentilla, cal. 8-fidus, pet. 4. j sem. subrotunda, nuda, receptaculo 

 parvo exsucco affixa." [Calyx 8-cleft, petals 4; seeds roundish, naked, 

 affixed to a small dry receptacle.] The characters given by Sir J. E. 

 Smith and Dr. Withering, although not exactly in the same words, do not 

 at all differ in sense. Dr. Withering says that he keeps them distinct, as 

 " more favourable for investigation :" see his Botanical Arrangement, ed. 3. 

 vol. ii. p. 476. 



