74 The Natural System of Botany. 



qualities which constitute a bird. Again, the form and ar- 

 rangement of the teeth of a quadruped afford almost unfailing 

 indications of the form of its digestive apparatus, of the na- 

 ture of its food, and of its general structure. In a similar 

 manner the botanist selects from the whole set of characters on 

 which his classification depends, those which afford the most 

 apparent marks, to distinguish one division from another. The 

 most natural character, then, as the distribution of the veins 

 of a leaf, is that which affords the most plain and extensive 

 information as to all the other characters of the plants to which 

 it is peculiar. The number of the stamens or styles indicates 

 comparatively nothing in this respect, and is therefore only an 

 artificial character. 



A second important principle of natural classification is 

 found in the fact that when a number of plants or animals are 

 collected according to their general resemblances, some indi- 

 viduals of the group will possess in a much higher degree than 

 the rest, the characters which are common to all, while others 

 will be so deficient in these characters as to seem hardly re- 

 lated to the same assemblage. Those members of a natural 

 group which most strikingly present an union of all the char- 

 acters by which it is distinguished, are called its types, and 

 those in which such characters are less obvious are termed 

 aberrant. By these latter is formed the connexion between the 

 different natural orders, since it is often the case that in the 

 aberrant members of an order, its characters become gradually 

 shaded off, until they almost blend with those of the next. To 

 refer to animals again, for an illustration, the family of Lizards 

 is intermediate between the Serpents and the Tortoises. The 

 body of some lizards is so elongated, and their legs so small, 

 as to render them nearly similar in appearance to snakes ; and 

 in one species the outer form is exactly that of a serpent, while 

 under the skin are found two pairs of very minute legs. This, 

 then, is an aberrant form, which it is scarcely possible to refer 

 with certainty to either family. On the side of the tortoises, 

 again, the lizards are connected by a species with the head, 

 neck, legs and tail of a lizard, but with a shell on its back. In 

 the vegetable kingdom instances of this kind will be frequently 

 met with, and therefore it by no means follows, when a plant 



