ANNOTATIONS AND ADDITIONS. 103 



which are the families to which, in different climates, the 

 greatest number of species belong. In a high northern 

 region, where the Compositse and the Terns are to the sum 

 of all the phsenogamous plants in the ratio of 1 : 13 and 

 1 I 25 (/. e. where these ratios are found by dividing the 

 sum total of all the Phanerogamse by the number of species 

 belonging to the family of Compositse or to that of Filices 

 or Perns), it may nevertheless happen that a single species 

 of fern covers ten times more ground than do all the species 

 of Compositse taken together. In this case Ferns pre- 

 dominate over Compositse by their mass, or by the number 

 of individuals belonging to the same species of Pteris or 

 Polypodium ; but they do not so predominate if we only 

 compare the number of the different specific forms of Filices 

 and Compositse with the sum of all the phsenogamous plants. 

 Since, then, multiplication of plants does not follow the 

 same law in all species, that is to say, all species do not 

 produce the same number of individuals, therefore the 

 quotients given by dividing the sum of the phsenogamous 

 plants by the number of species belonging to one family, do 

 not suffice by themselves to determine the character of the 

 landscape, or the physiognomy which Nature assumes in 

 different regions, of the earth. If the attention of the 

 travelling botanist is engaged by the frequent repetition of 

 the same species, their mass, and the uniformity of vegetation 

 thus produced, it is even more arrested by the rarity or in- 

 frequency of several other species which are valuable to 

 mankind. In tropical regions, where the Rubiacese, Myr- 

 taceae, Leguminosse, or Terebinthacese, form forests, one is 



