CHAPTER III 



THE NUMEEICAL DISTRIBUTION OF BRITISH PLANTS I TEMPERATE 



FLORAS COMPARED 



Proceeding from the more to tlie less familiar regions we 

 will be^rin witli a few of the facts as to the flora of our own 

 country. Partly owing to its insular character, and also be- 

 cause it has few lofty mountains or extensive forests, the num- 

 ber of species of flowering plants is somewhat (but not much) 

 below that of most continental countries of equal area. It con- 

 tains about 1800 species, as a rough mean between the estimates 

 of dift'erent botanists.^ It may seem curious that there should 

 be any such difference of opinion, but one of the facts that 

 have alwa^^s been adduced as showing that species are not fixed 

 and immutable entities is the frequent occurrence of varieties, 

 which are sometimes so peculiar and so apparently constant 

 that they are treated by some botanists as distinct species, by 

 others as sub-species, and by others again as forms or varieties 

 only. These modifications of a species are usually confined to 

 a more limited area than the species itself, and are occasionally 

 connected with each other or with the parent species by inter- 

 mediate forms. Again, when these varieties are cultivated, 

 and esjDecially when a large number of plants are raised from 

 their seeds, they are apt to revert partially or wholly to the 

 parent form. Another source of difference of opinion among 

 botanists is, as to the treatment of those plants, found usually 

 near human habitations, which are supposed to have been orig- 

 inally introduced, either purposely or accidentally, from foreign 

 coimtrios. Such are the wild Larks])ur and Monkshood, the 



1 In all the tables and comparisons of " Ploras " in this work, unless 

 where ferns are specially noted, flowering plants only are intended, even 

 when the term '* plants " is used. 



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