797 



the Lake Province, and the North and West Highlands, are still in- 

 completely made out ; and there are several dubious species, whose 

 provincial distribution can be very imperfectly known at present. The 

 number of un-enclosed figures in the first line, in contrast with the 

 number given as the estimate, will show where additions have been 

 made to the latter, on assumed probabilities. For counties, the esti- 

 mated number will often be given much higher than has been actually 

 ascertained ; more especially for the common species, which are sel- 

 dom noticed, except in local floras and catalogues which profess to 

 include everything. The census for counties is estimated by, first, 

 reckoning up those within which the species has been ascertained to 

 occur ; secondly, reckoning those from which it is believed to be ab- 

 sent; and, thirdly, adding the rest to one or other side, according to 

 presumed probabilities. Though much is here assumed, particularly 

 with respect to the distribution of the common species, yet the result 

 of this estimate, it is believed, will come very near the truth ; the 

 author's attention having been so long directed to the distribution of 

 plants in Britain, that he can usually guess pretty accurately whether 

 any given species will or will not be found in any given county. Of 

 course, there are some exceptions to the accuracy of such guesses, 

 especially in the cases of confused or neglected species, such as 

 CEnanthe peucedanifolia or Ranunculus Lenormandi. As an exam- 

 ple, where much has been assumed without certain knowledge, the 

 census of Stellaria media may be cited. On putting together all his 

 local lists, the author cannot show, on authority, that this very com- 

 mon plant grows in so many as sixty counties ; but he unhesitatingly 

 assumes it to occur in every county. The whole number of counties 

 is taken at 82; some small counties (Rutland, Kinross, &c.) being 

 sunk into those adjacent, and some isles or groups of isles (Man, 

 Hebrides, &c.) being reckoned as counties of themselves. The inter- 

 mediate numbers, between 15 and 80, are taken in steps of 5 or 10, 

 since the use of units would there be only an affectation of exactness ; 

 and the nature of the test throws the larger proportion of the species 

 towards one or other extreme of the scale. The series of numbers 

 actually used in the census of counties runs thus : — 1, 2, 3, 4, 5, 6, 7, 

 8, 9, 10, 12, 15, 20, 25, 30, 40, 50, 60, 70, 75, 80, 81, 82. 



" The fifth line indicates the range of latitude and the geographic 

 type. To show the limits in latitude, those figures are used which 

 correspond with the mathematical lines on maps, between which all 

 the known localities are situate. No fractions of degrees are used. 

 Thus, in marking the range of Clematis Vitalba, as 50 — 53, it is not 

 Vol. n. 5h 



