274 \I. EXPLANATIONS OF THE 



4. Explanations of the Census. 



The preceding 'Census of Species' may be regarded and explained 

 under tbree aspects. First, the numbers whicb precede the names of 

 the plants may be said to constitute tbe general census for totul Britain. 

 Secondly, the numbers which succeed the names, in the columns headed 

 by the initial letters S N W Sc E, give a more local or partial census, 

 presently to be explained. Thirdly, repetitions of some of the specific 

 names at the end of several of the lines. Further, three summaries are 

 added at the end of the general list of plants, showing the numbers of 

 the species in relation to the numbers of the provinces and other sub- 

 divisions. 



First. — The names of the plants are repetitions of those before enu- 

 merated in the ' Summary of Distribution.' They succeed each other 

 in accordance with the relative frequency of the plants, one compared 

 ■with another, as closely as that condition or character can be exhibited 

 by aid of the test resorted to. The plants are first divided into 38 

 groups, in accordance with the number of the subprovinces in whicb 

 they have been ascertained to occur, or are found reported on reliable 

 authority. The plants in each of the 38 groups are ne.Kt arranged in a 

 series according to the number of counties and vicecounties, as indicated 

 by the number prefixed to each. And in cases where the number of 

 subproviuces and counties is the same for two or more species, then the 

 number of primary provinces is taken to determine the position of the 

 names in the series; but it has not been deemed requisite to introduce a 

 second column of prefixed nos. for the sole purpose of showing the num- 

 ber of those provinces. Further, in cases where the number of primary 

 provinces is also equal for two or more plants, then various other 

 circumstances have been resorted to, as tests or measures of relative 

 frequency ; for instance, the altitudes attained and the greater or less 

 probability of other habitats being discovered, &c. &c. The series thus 

 worked out is numbered from 1 to 1425 by means of numbers set after 

 the shorter names only, for typographical convenience ; the proper nos. 

 for the intermediately placed names being easily known by reckoning 

 from those which are so inserted. 



It is made obvious by the prefixed nos., that the plants would have 

 been somewhat diflfereiitly grouped together, if the number of counties 

 and vicecounties had been taken as the leading test, by first dividing the 

 whole flora into 99 groups (the largest number of counties ascertained 



