102 



TAXONOMY. 



nera, in the natural arrangement, are not correctly placed, — 

 that they ought much rather to be considered as Families, and 

 their subdivisions raised to the rank of genera. This has hap- 

 pened in our days with the genera Lichen^ Fucus, and Pj'o- 

 tea, which have justly been expanded into several genera, ac- 

 cording to fixed characters. 



153. 



Many genera consist of such numberless species, that it is 

 much to be wished they were separated into a greater number 

 of genera. But so long as Nature shews a correspondence 

 in essential parts, we dare not separate what she has united. 

 The genera Aster, Erica, Mesemhryanthemum, Salvia, and 

 some others, thus justly remain undivided, and we must only 

 endeavour to arrange the species in such a manner as is 

 required by their natural correspondence. 



This arrangement into divisions or sections, is as necessary 

 in numerous genera, as the arrangement of the genera them- 

 selves according to a certain principle of affinity. Not only 

 the outward view of the arrangement, but the investigation 

 of it, is generally relieved by this means. Many of these sec- 

 tions, if we were to carry our distinctions to a great length, 

 especially in the genera Convallaria and Polygonum, might 

 become as many genera, especially as they are separated from 

 each other not merely by numerical proportion of parts, but 

 by other marks. Sometimes we give peculiar names to these 

 sections, as the genus Polygonum is divided into Atraphexoi- 

 dae, Bistortae, Persicariae, Polygona, and Helxinae. Otherwise 

 these sections are denoted by the signs * or -f-. 



III. Idea of Tribes and Families, 

 154. 



As in the animal kingdom there are related genera which 

 form tribes, as the Cetaceous Animals^ the Marsh Fowls, and 

 the Graminivorous Animals, we also find in the vegetable 

 world a multitude of related genera, which together form 



