358 



manner vary, according to the views of the party by whom the esti- 

 mate might be made. " By rigidly excluding all species not fully 

 recognised as indigenous, and also numerous varieties which are com- 

 monly now counted amongst species, the flowering plants of Britain 

 will be found scarcely to exceed 1200; or, admitting doubtful species, 

 but still excluding doubtful natives, they may be taken at 1400. To 

 reach the number of 1636, given in the Catalogue printed by the Bo- 

 tanical Society of Edinburgh,* we must admit many species of foreign 

 introduction, and a goodly list of varieties named and received as spe- 

 cies." But in determining the proportion borne by the ferns to the 

 flowering plants, " if we take a low estimate for one group, we must 

 follow the same rule in the other, or their proportions will unavoidably 

 appear wide of truth." The proportions of the two groups taken from 

 the three estimates of the number of each given above, will be these. 



"ferns. flowers. proportions. 



36 1200 1 to 33i 



40 1400 1 to 35 



44 1636 1 to 37" 



The author by way of comparison next gives a table showing the 

 relative numbers of ferns and flowering plants in eight different Floras ; 

 the proportions (omitting fractions) being as under. 



Iceland 1 to 25 Channel Isles 1 to 51 Sweden I to 40 



Faroe 1 to 27 Belgium 1 to 67 Lapland 1 to 25 



Ireland I to 30 Zealand 1 to 47 



" Ferns are thus seen to bear a larger proportion relatively to flowering plants, in 

 the northern and mountainous parts of Western Europe, than is the case with this 

 group of plants in low countries, — such as Belgium, Zealand, and the Channel Isles, 

 — ^whose latitude nearly corresponds with that of England ; whilst the proportions he- 

 fore set down for Britain place it in the scale betwixt Faroe and Iceland, on the one 

 hand, and Belgium and the Channel Islands on the other; the former having a rela- 

 tive predominance of ferns, the latter having a similar predominance of flowering 

 plants." — p. 91. 



It is then shown by a comparison of twenty local Floras, that the 

 distribution of ferns in Britain corresponds with their distribution in 

 the north-west of Europe generally, since both the relative and abso- 

 lute number of species diminish " as we pass from the hilly districts of 



*The 1st edition of the Catalogue is here refeiTed to ; the number of species (1636) 

 given in the " Enumeration of Plants " prefixed to the Catalogue appears to include 

 the ferns as well as flowering plants. In the 2nd edition the number of species in the 

 two groups is distinctly given us 1594 and 55, (including Lycopodium, Isoetes, Pilu- 

 laria and Equisetum). 



