294 PHYSIOGNOMY OP PLANTS. 



of the earth's surface. (Compare my memoir, entitled "De distribu- 

 tione geographica Plantarum secundem coeli temperiem et altitudinem 

 montium, 1817, pp. 24-44 ; and the farther development of the sub- 

 ject of these numerical relations given by me in the Dictionnaire des 

 Sciences naturelles, t. xviii. 1820, pp. 422-436; and in the Annales 

 de Chimie et de Physique, t. xvi. 1821, pp. 267-292. 



The numerical relations of the forms of plants, and the laws ob- 

 served in their geographical distribution, may be considered in two 

 very different ways. If plants are studied in their arrangement 

 according to natural families, without regard to their geographical 

 distribution, it is asked, What are the fundamental forms or types 

 of organization to which the greatest number of species correspond? 

 Are there on the entire surface of the earth more Glumaceae than 

 Composites? Do these two orders make up between them one-fourth 

 part of the whole number of phaenogamous plants? What is the 

 proportion^ of Monocotyledons to Dicotyledons? These are questions 

 of General Phytology, or of the science which investigates the organi- 

 zation of plants and their mutual connection, or the present state of 

 the entire vegetable world. 



If, on the other hand, the species of plants which have been 

 grouped according to the analogy of their structure are considered, 

 not abstractedly, but according to their climatic relations, or accord- 

 ing to their distribution over the surface of the earth, .we have ques- 

 tions offering quite another and distinct interest. We then examine 

 what are the families which prevail more in proportion to other 

 Phanerogamse in the torrid zone than towards the polar circle ? Are 

 Composites more numerous, either in the same geographical latitudes 

 or on the same isothermal lines, in the New than in the Old Con- 

 tinent? Do the forms which gradually lose their predominance in 

 advancing from the Equator towards the Poles follow a similar law 

 of decrease in ascending mountains situated in the equatorial regions ? 

 Do the proportions of particular families to the whole mass of Pha- 

 nerogamae differ in the temperate zones, and on equal isothermal 

 lines, north and south of the Equator? These questions belong pro- 

 perly to the Geography of Plants, and connect themselves with the 

 most important problems of meteorology and terrestrial physics. 

 The character of a landscape or country is also in a high degree 



