196 The Scottish Naturalist. 



already given in the subject ; a proposition is real when the pre- 

 dicate adds something to what the subject already contains. 

 Thus, when I say "knowledge is certain perception," I simply 

 unfold the meaning of the word knowledge ; but when I assert 

 that " knowledge is power," I here predicate something of know- 

 ledge which is not included in the mere conception of it : know- 

 ledge and power are in themselves two entirely different notions, 

 and by bringing them together, and affirming the one of the other, 

 I state new truth, I give additional information. Obviously, the 

 one kind of proposition (the verbal) simply tells us what a tiling 

 (the subject of the proposition) is; the other (the real) goes 

 farther, and tells us something about that thing. The latter is, 

 strictly speaking, informational ; the former is not. 



Now, a distinction similar to this has to be drawn between the 

 two parts of the biological "mark." So much of it is simply 

 the analysis of the particular group in question, and, therefore, 

 answers to the verbal proposition ; but so much of it is informa- 

 tional, and is thus a real predicate. And these two parts ought 

 not to be jumbled together. 



For the sake of clearness, let us revert for a moment to the 

 botanical "characters" that have hitherto occupied our attention. 

 They are all strictly definitions. The Ordinal mark of the 

 Ranunculacere, for instance (p. 157), is just the assemblage of 

 characters that distinguish the Ranunculus family. But when I 

 proceed further and say — " This order prefers a cold damp 

 climate ; has such and such a geographical distribution ; numbers 

 so many species; has acrid, caustic properties, more or less 

 poisonous, very volatile in the foliage and the herbaceous parts, 

 sometimes very virulent in the roots ; possesses certain affinities 

 with the Papaveracese, Berberidaceoe, &C, and shows certain 

 resemblances to the Rosacea^ the (monocotyledonous) Alis- 

 macese, &c.," I go beyond mere definition, and the kind of 

 information I now give should be carefully separated from my list 

 of purely defining characters. 



In the best botanical works, this separation is distinctly made. 

 See, for example, the Genera Pla7itarum already referred to, or 

 Lindley's Vegetable Kingdom, or almost any of the chief authorities. 

 But certain defects are still apparent in the working out of the 

 distinction, and it may not be out of place, before concluding, to 

 call attention to these. 



The informational part of the mark consists, according to 

 current usage, of these four things — geographical distribution, 



