324 TAXONOMY. 



Chestnut. Familiar illustrations of genera in the animal king- 

 dom are furnished by the Cat kind, to which belong the domestic 

 Cat, the Catamount, the Panther, the Lion, the Tiger, the Leop- 

 ard, &c. ; and by the Dog kind, which includes with the Dog 

 the different species of Foxes and Wolves, the Jackal, &c. The 

 languages of the most barbarous as well as of civilized people 

 everywhere show that they have recognized such groups. Natu- 

 ralists merely give to them a greater degree of precision, and 

 indicate what the points of agreement are. 



643. If most genera were as conspicuously marked as those 

 from which these illustrations are taken, genus would be as defi- 

 nitely grounded in nature as species. But popularly recognized 

 genera, rightly based, are comparatively few. Popular nomen- 

 clature, embodying the common ideas of people, merely shows 

 that generic groups are recognizable in a considerable number 

 of cases, but not that the whole vegetable or the whole animal 

 kingdom is divisible into a definite number of such groups of 

 equally or somewhat equally related species. The naturalist 

 discerns the ground of genera in characters which the casual and 

 ordinary observer overlooks ; and, taking the idea of genera 

 from the numerous well-marked instances as the norm, applies 

 it as well as possible to the less obvious or less natural cases, and 

 groups all known species under genera. Resemblances among 

 the species when rightly grouped into genera, though real, are 

 often so unequal in degree, that certain species may be about as 

 nearly related to neighboring genera. So that the recognition of 

 genera even more than of species is a matter of judgment, and 

 even of conventional agreement as to how and where a certain 

 genus shall be limited, and what particular association of species 

 shall hold the position of genus. All the species of a genus must 

 accord in every important structure ; but extended observation 

 only can settle the question as to what are important and what 

 are incidental characters. For example, the pinnatifid or sinu- 

 ate leaf might have been thought as essential to the Oak genus 

 as the acorn-cup ; but many Oaks are now known with entire 

 leaves, resembling those of Willow or Laurel. An open acorn- 

 cup beset with imbricated scales is a character common to all 

 European and American Oaks ; but in numerous Asiatic species 

 the cup bears concentric or spiral lamellae instead, and in others 

 the cup takes the form of a naked and closed sac. Maples have 

 palmately- veined and lobed leaves ; but one species has undi- 

 vided and pinnately-veined leaves. The Apple and the Pear 

 under one view are of the same genus, under another they rep- 

 resent different genera. 



