28 Mr. R. B. Hinds on Geographic Botany. 



When a group of plants is discoverable only in one of the 

 great divisions or regions, it will be convenient to apply to it the 

 term monomic, as expressive of its geographic properties; thus 

 Vochyacece, being confined to South America, is a monomic 

 family ; and Cliffortia, whose shrubby species are all indigenous 

 to South Africa, is a monomic genus. On the other hand, a 

 natural family common to all the divisions, and these are about 

 a third of the whole, are called polynomic ; and a genus with a 

 similar range, as Viola or Ranunculus, is a polynomic genus. If 

 a group is restricted to two or more of the divisions, the appro- 

 priate Greek numeral must be substituted; thus Acerineee, the 

 members of which are natives of the temperate and sub-tropic re- 

 gions of Europe, Asia and North America, is a trinomic family. 



The value of the generic character is 10"6 ; an amount the re- 

 sult of an extensive estimate, though not of the whole vegetable 

 kingdom, which unfortunately is not within our reach at present 

 in a satisfactory form. This may however be considered as very 

 closely approaching correctness, and giving us a tolerable accurate 

 notion of the importance of the genus ; compared with some of 

 the statistical details which have become cui'rent of late years, it 

 must be allowed to stand on a much firmer and broader founda- 

 tion, and therefore not less worthy of faith. If all the species 

 then were equally distributed among the genera, the share that 

 would fall to each would be about ten and a half; but the ge- 

 nera are not so regularly composed, and when studying a very 

 bulky or a small genus, the average shows us how far the group 

 under consideration departs from the standard. The smaller 

 genera greatly prevail, whilst some of the largest possess a great 

 multitude of species. Those which contain but a single species 

 bear a great proportion to the others, which I am disposed to 

 think will diminish when the afiinities of the genera to each other 

 are better understood. 



At the same time that some of these trifling genera become 

 merged into others, it is highly probable that the more extensive 

 will undergo analysis, leaving the average proportions very slightly 

 affected. A few of the largest genera at present are. Pelargonium 

 with 369 species, Mesembryanthemum 316, Acacia 258, Loranthns 

 251, Astragalus 244, Silene 217, Cassia 2\\. 



