DISTRIBUTION OF PLANTS. 9 



time, the Linnaean and the Jussisean, some- 

 times, though unfairly, termed the artificial 

 and the natural methods ; both are useful, the 

 former having been aptly designated as " the 

 grammar," the latter as " the literature " of the 

 science, and both should be studied. 



III. GEOGRAPHICAL BOTANY. This, which 

 will form the subject of our remarks, is the 

 investigation into those laws which regulate the 

 distribution of plants over the face of our 

 globe \ which assign a certain set of plants 

 to one country, and a different series to 

 another ; or, which allow of one plant being 

 so widely distributed over the various coun- 

 tries of our globe as almost to be called 

 universal, while others are restricted to the 

 narrowest limits. 



It is estimated that the number of distinct 

 species of plants, already known and described, 

 is 92,930. This includes all the flowering 

 plants, trees, and shrubs, ferns, mosses, lichens, 

 sea and river weeds, (Algce,) mushrooms and 

 their allies, (Fungi j) in fact, every vegetable 

 production. These are very variously distri- 

 buted over our globe ; light, heat, altitude, 

 soil, situation, all contributing their influence 

 in modifying the diffusion of species, and of 

 these the first two are by far the most impor- 

 tant. Near the equator, where light and heat 

 are most intense, vegetation is most luxuriant 

 and profuse ; while at the poles, or at those 

 high elevations which reach above the line of 

 perpetual snow, or in the profounder recesses 



