193
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��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 W. 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 which 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
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