IV. EXPLANATIONS, ETC. 317 



to be understood by the vowels ; the nos. being the lines of longitude 

 that bouud ..nd divide the spaces : — 



West 8a6e4i2o0u2 East. 

 As the first vowel is never required for longitudes in South Britain, in 

 the absence of any list of plants for the Scilly Isles, a dot or blank is 

 always interposed between the other vowels and the last of the fig, ires 

 which denote the provinces ; confusion between the figures and letters 

 being thus fortunately prevented. 



General Species. — The plants of the second divisional list (page 302) 

 difi"er from those enumerated in the latter portions of the first by one 

 particular only. They are still plants which extend northward beyond 

 the latitudinal line of 57, but which differ from those previously enume- 

 rated by having been ascertained to occur continuously in provinces 

 1 to 16, 1 to 17, or 1 to 18 ; that is, they are found in all the interme- 

 diate provinceo without exception. Other species which extend north- 

 ward of 57, and into provinces 16, 17, 18, as the case may be, have the 

 provincial continuity of their distribution interrupted by one or more 

 vacant provinces, as shown in the first divisional list. Many of such 

 vacancies are doubtless only temporary ; arising solely from the incom- 

 pleteness of present knowledge. Eventually, the filling in of such 

 vacancies will remove various species from the first into the secand 

 division. Thus, on page 299 Briza media and Genista anglica are indi- 

 cated in provinces 1 to 17, with the single exception or vacancy of 16. 

 If they can be certainly ascertained to occur also in the latter province, 

 as is very probable, the con)pleteness of their provincial continuity will 

 then remove them into the corresponding group of the second or 

 general division. By thus restricting the groups of " general species,'' 

 so as to include only those with a non-interrupted provincial distribution 

 actually ascertained, many needless repetitions of the same series of 

 figures are avoided, and the lists of names can be compressed into a 

 third of the space, by placing three on each line ; — the practical conve- 

 nience before adverted to, on page 314. For the most part, however, 

 these general species do also attenuate more or less northward ; that is, 

 they cease altngether, or become scarcer or less certainly native, beyond 

 latitude 57 or 58, in Orkney or Shetland. Some few of them, on the 

 contrary, approximate in their distribution to the third division, that of 

 boreal plants, by having greater frequency in the north than in the 



