in. FLORA OF BRITAIN. 405 



approach towards an equality of numerical jiroportions in 

 different countries, than the smaller (genera-like) orders 

 are found to present. 



Compositce and Gramiiia, for example, occur ever}^- 

 where ; and in many of the most thoroughly examined 

 countries, they constitute somewhere about the same por- 

 tion or proportion of the aggregate flora. It is much 

 otherwise with orders of more average numerical values, 

 and which are more truly groups of genera ; for example, 

 Saxifragacece and Oxaiiclacece, slightly above average ; — 

 Gentianacece and Geraniacece, more decidedly above ; — 

 Primulacece and CucurhitacecB, below an average, in re- 

 spect to number of included species ; — the numbers and 

 proportions of all these being widely dissimilar in various 

 countries. Such dissimilarities are not to be found in 

 the great groups like Compositce and Gramina, but occur 

 in their "sub -orders " ; these latter being truly more on 

 equality with the middling and the smaller orders, in 

 respect to their structural and physiognomical distinc- 

 tions, than the gi-eat groups are. The great leading 

 orders may suffice for general (rather vague) comparisons 

 between countries widely dissimilar in geograjihical posi- 

 tion and climate ; but they avail very badly for bringing 

 into view those slighter differences in the flora and vege- 

 tation which are to be found between adjacent countries. 



Here comes a practical difficulty for a writer on i^hj'to- 

 geography. It is tedious and confusing, to attempt 

 verbal comparisons carried through the whole series of 

 orders. Selection becomes necessary ; whether it is 

 wished to show the ordinal relation which the flora of 

 this country bears to that of the earth generally, or to 

 any portion of it, — or it is wished only to institute com- 

 parisons between the orders in Britain itself, aj)art from 

 other countries. But it is not easily determined what 



