ni, FLOBA OF BRITAIN. 407 



respectively 1227, 152, 46 species. As somewhat similar 

 ordinal disproportions occur in the floras of other countries 

 also, it is evident that ordinal comparisons can he insti- 

 tuted, which will prove much more comprehensive than 

 those embracing only half of the species, and yet not 

 requiring the enumeration of more than a fourth or a 

 third of the orders themselves. Opinions may differ, 

 whether the rule of selecting those orders which contain 

 or exceed the average number of species, may be the best 

 medium coiu-se to take ; but it seems to meet the object 

 above adverted to. 



It has been shown on page 396, that the average num- 

 ber of species to an order, in this island, is about a 

 medium fraction between 14 and 15. Only 23 of the 

 orders exceed this average ; and 5 more fall short of the 

 average by the fraction only. All the remaining 70 

 orders include fewer than the average number of species. 

 — Nearly the like proportions are found in Scandinavia, 

 where 26 orders exceed the average of 16 species with a 

 small fraction ; 1 more falling short of it by the fraction 

 only. — In Middle Europe 28 orders equal or exceed the 

 average ; which is there about 39 species to an order. — 

 According to the Sylloge before quoted, 28 orders in the 

 European flora exceed the average number of species ; 

 there rising to 74, less a small fraction. — In the vegetable 

 kingdom at large, where the orders are more than doubly 

 numerous, there may be twice as many which exceed the 

 average number of species, rising to neai-ly 300 ; but the 

 estimates cannot be held sufficiently exact or true, those 

 for one order compared with those for another, to allow 

 of any precise number or proportion being named and 

 relied upon. 



Another rule of selection might perhaps keep the 

 selected orders more nearly on numerical equality ; 



