The Scottish Naturalist. 195 



and Vascular Cryptogams is contained in cabinets below one of the 

 table cases, and is already rather extensive, all the Perthshire species, 

 with very few exceptions, having been obtained. The specimens are 

 glued down upon ordinary herbarium paper. In a private collection 

 it is perhaps not desirable to fasten the specimens, but in a public 

 collection this is necessary to prevent their being injured. As in 

 the other departments, it is intended to illustrate, as fully as 

 possible, the local distribution by specimens ; and already many 

 species have a long series of illustrative examples. Collections 

 of the other orders of cryptogamic plants are being formed, but 

 there has not yet been time to arrange them. In addition to the 

 herbarium, a collection of the indigenous timber trees of Perthshire 

 is being at present arranged in a series of wall cases. The trees, 

 including the larger shrubs, are about twenty in number, and each 

 is (or will be) represented as follows: — (1) A longitudinal cut, about 

 3 feet long, to show the bark ; (2) a polished plank, about 3 feet 

 long, to show the nature of the wood ; (3) a polished cross section 

 of the trunk ; (4) a young branch to show the arrangement of the 

 twigs and buds; (5) specimens of the leaves, flowers, and fruit — 

 the latter, if necessary, in liquid ; (6) specimens of the wood, &c, 

 showing injuries by insects, &c. ; (7) specimens of the chief 

 insects and fungi which are injurious to the tree ; (8) a photograph 

 of a Perthshire specimen of the tree. All the specimens are of 

 course accompanied by explanatory labels. 



Though a number of specimens have been accumulated, no 

 permanent arrangement has yet been made in the geological and 

 mineralogical department. A representative collection will be 

 exhibited on sloping shelves in a high case, and the main collec- 

 tion will be kept in drawers in cabinets. In illustration of the 

 local geology, the walls of the museum above the cases afford an 

 opportunity for the display of drawings of sections, of which 

 several are already in position and others are being prepared. 



THE SCIENTIFIC METHOD IN BIOLOGICAL CLASSIFICATION. 

 By Rev. WILLIAM L. DAVIDSON. 



I. DEFINITION. 



THERE is a distinction of no slight importance drawn by 

 logicians between a "verbal" and a "real" proposition. 

 A proposition is verbal when the predicate simply unfolds what is 



