OF CENTRAL AFRICA. 263 



seem to imply that in the embryo of this family the posi- 

 tion of the radicle is variable, and that of the- cotyledons 

 fixed. It is at least deserving of notice that the reverse of 

 this is the fact ; though it is certainly not necessary to 

 change these terms, which are now generally received. 



On the subject of Savignya, two questions naturally pre- 

 sent themselves. In the first place — Is this genus, solely 

 on account of its conduplicate cotyledons, to be removed 

 from Alyssineae, where it has hitherto been placed, to Vellese, 

 its affinity with which has never been suspected, and to whose 

 genera it bears very little external resemblance ? Secondly 

 — In dividing Cruciferaj into natural sections, are we, with 

 M. De Candolle, to expect in each of these subdivisions an 

 absolute uniformity in the state of the cotyledons ? As 

 far as relates to the accumbent and flatly incumbent states, 

 at least, I have no hesitation in answering the latter ques- 

 tion in the negative ; and I believe that in one case, namely, 

 Hutchinsia, these modifications are not even of generic im- 

 portance, for it will hardly be proposed to separate H. 

 alpina from petraea, solely on that ground. I carried this 

 opinion further than I am at present disposed to do, in 

 the second edition of Mr. Alton's 'Hortus Kewensis,' where 

 I united in the genus Caldle plants, which I then knew to 

 differ from each other, in having accumbent and condupli- 

 cate cotyledons ; and I included Capsella bursa-pastoris in 

 the genus Thlaspi, although I was aware, both from my 

 own observations and from Schkuhr's excellent figure,^ 

 that its cotyledons were incumbent. I am at present, [sia 

 however, inclined to adopt the subdivision of both these 

 genera, as proposed by several authors and received by 

 M. De Candolle ; but to this subdivision the author of the 

 ' Systema Naturale ' must have been determined on other 

 grounds than those referred to ; for in these four genera, 

 in which the three principal modifications of cotyledons 

 occur, he has taken their uniformity for granted. 



As to the place of Savignya in the natural family, I be- 

 lieve, on considering the whole of its structure and habit, 

 that it ought to be removed from Alyssinese to a subdivision 



' S'f'wW, &A, 180, 



