193 



#ricjinul %xiuhB. 



ON BRASSICA POLTMORPHA, Si/me. 

 By W. T. Thiselton Dyer, B.A., B.Sc. 



In two papers in this Journal (vii. 346-350 ; viii. 869-372) Mr. H. C. 

 Watson has described a Brasska which occurs by the Thames-side in 

 Surrey and Middlesex, and which he believes to be B. campestris, L. ; 

 understanding by that name the " wild stock of the Turnip." In the 

 ' Flora of Middlesex ' (p. 35) this plant was erroneously placed under 

 B. Naptis, L. ; an error which arose from Dr. Trimen and myself having, 

 in the absence of such opportunities as Mr. Watson possesses of ex- 

 amining the winter-tufts, followed Dr. Boswell S^-me, who had recorded 

 under that name plants from the Thames-side. Mr. Watson has, how- 

 ever, abundantly demonstrated that the Thames-side Brassica is perfectly 

 distinct from B. Nap/i-i, and that it is in fact what, adopting the characters 

 given by De Candolle (Syst. Nat.), Smith (Eng. FL), Boswell Svme, 

 (Eng. Bot.), Hooker (Stud. EL), and Boreau (Fl. du Cent, de la *Fr.), 

 would be called a wild state of B. Rapa, L. 



A perfectly distinct question, therefcu'e, from the identity of the 

 Thames-side species is raised by Mr. Watson with respect to the syno- 

 nymy of the other plants allied to it. Hitherto, most systematic books 

 in this country have included three allied species o{ Brassica admitting of 

 being distinguished by characters drawn from their radical leaves. Using 

 the language of De Candolle (Reg. Veg. Syst. Nat. ii. 588-592), these 

 characters may be stated as follows : — 



B. cajiipeslris, foliis polline glaucis inferioribus novellis subhispidis. 



B. Rapa, foliis radicalibus lyratis polline glauco destitutis setoso- 

 scabris, 



B. Napus, foliis glabris polline csesio glaucescentibus. 



Substantially the same characters are given by Smith (Eng. Fl. iii. 217, 

 218) ; who, however, also describes campestris as having radical leaves, 

 only " rather glaucous, rough all orer\x'\i\\ minute bristly hairs ' (p. 219), 

 which looks as if he were not wholly free from some confusion between 

 this plant and his Rapa. Lindley ('Synopsis') merely quotes Smith. Sir 

 VV. Hooker (Brit. Fl. 308) refers to Smith, and has the same arrange- 

 ment, but does not mention the green radical leaves of B. Rapa, distin- 

 guishing it from B. carnpeslris by its fleshy root instead. Boreau gives 

 the sane characters as De Candolle. 



The nomenclature of probably all modern English writers, who have 

 treated of the economic aspect of these plants, is borrowed from 

 De Candolle's determinations. Unless on very urgent grounds, it would 

 be hardly desirable to alter this. The reform, unfortunately, of scientific 

 terms wliich have got into popular use rarely has any other effect than to 

 make both old and new ambiguous and useless. The old and erroneeus 

 meanings continue to survive alongside with the new and correct ones. 

 It is always best, when popular use has spoiled a term, to Icive it to its 

 fate, accept it in its erroneous sense, and, if necessary, invent a new 

 word to do its proper work. 



Of each of the three cultivated species of Brassica De Candolle 



VOL. IX. [jULY 1, 1S71.] O 



