ANNOTATIONS AND ADDITIONS. 295 



dependent on the predominance of particular families of plants, 

 which render it either desolate or adorned, smiling or majestic. 

 Grasses forming extensive savannahs, Palms and other trees afford- 

 ing food, or social Coniferse forming forests, have powerfully influ- 

 enced nations in respect to their material condition, to their manners, 

 to their mental dispositions, and to the more or less rapid develop- 

 ment of their prosperity. 



In studying the geographical distribution of forms, we may con- 

 sider species, genera, and natural families, separately. In social 

 plants, a single species often covers extensive tracts of country; as 

 in northern regions forests of Pines or Firs and extensive heaths 

 (ericeta), in Spain cistus-covered grounds, and in tropical America 

 assemblages of the same species of Cactus, Croton, Brathys, or 

 Bambusa Gruadua. It is interesting to examine these relations more 

 closely, and to view in one case the great multiplicity of individuals, 

 and in another the variety of organic development. We may in- 

 quire what species produces the greatest number of individuals in a 

 particular zone, or we may ask which are the families to which, in 

 different climates, the greatest number of species belong. In a high 

 northern region, where the Composite and the Ferns are to the sum 

 of all the phsenogamous plants in the ratio of 1 : 13 and 1 : 25 

 (i. e. where these ratios are found by dividing the sum total of all 

 the Phanerogams by the number of Species belonging to the family 

 of Compositse or to that of Filices or Ferns), it may nevertheless 

 happen that a single species of Fern covers ten times more ground 

 than do all the species of Composites taken together. In this case 

 Ferns predominate over Composite by their mass, or by the number 

 of individuals belonging to the same species of Pteris or Polypo- 

 dium ; but they do not so predominate if we only compare the 

 number of the different specific forms of Filices and Composite 

 with the sum of all the phsenogamous plants. Since, then, multipli- 

 cation 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 phseno- 

 gamous 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 



