IV. EXPLANATIONS. 347 



whicb are always to be read witL the qualifying phrase of " more or less" 

 in the mind of the reader. 



Illustrations of the sort of uncertainty intended, and the need of 

 keeping in mind the qualifying "more or less," might be obtained 

 within the compass of this volume, on rigidly comparing the heights 

 indicated in the ' Summary of Distribution' (by the letters "c a u") 

 with the limits stated in the list here under explanation. It has been 

 fiually arranged for printing since the ' Summary ' was all printed off; 

 some few of the altitudes being slightly altered on re-calculation, or on 

 account of some additional locality, not taten into account while the 

 ' Summary ' was under preparation for the press. For example, Vale- 

 riana officinalis and Carduus heterophyllus are not marked by the letter 

 'u' in the 'Summary,' as belonging to the upper stage of altitude: 

 while on page 329 their upper limits are carried to 720 yards ; and they 

 might consequently have been held to inhabit the upper stage, or that 

 between 700 — 1400 yards. In volume second they were carried up to 

 650 and 700 yards ; steps of less than 50 yards being seldom made in 

 the former volumes ; and hence they were not lettered for the upper 

 stage. 



Notes on the altitudes attained by the Hieracia, taken at inter^-als 

 during a score of past years, are of course inapplicable to the more 

 segregated species recently published in the Monograph by Mr. Back- 

 house. The altitudes given by this gentleman are therefore substituted; 

 his list of species having been incorporated in the ' Summary of Distri- 

 bution ' with one exception and one addition. It is suspected, however, 

 that the altitudes stated in the book of Mr. Backhouse can be intended 

 only as very rough guesses ; and that they have in no case been ascer- 

 tained through instrumental observation. Perhaps they are quite as 

 true and reliable as the so-called species themselves ; which no botanist 

 seems able to make out by the diffuse and non-contrasting descriptions 

 in the book ; although Mr. Backhouse can himself doubtless label most 

 specimens empirically in close accordance with his own nomenclature ; 

 — much as an amateur florist can point out well enough his dukes and 

 lords, gcvcrals and admirals, superbs and dijiances, among his rose.«, 

 tulips, dahlias, and other fancy flowers; though botanists are unable to 

 express their trivial differences in au intelligible manner by the lan- 

 guage of science. 



Dr. Dickie published a series of altitudes for the plants of Aberdeen- 

 shire, iu the second volume of the Loudon Journal of Botany, pages 



