FORMATION OP ORDERS AMD CLASSES. 317 



the number of objects, which the Botanist has to study, remains 

 by far too great for convenience ; and he next forms his genera 

 into orders, and combines these orders into classes^ according to 

 their respective correspondence and difference in certain charac- 

 ters of a still more general nature. Now in this process he may 

 follow two very different plans ; and upon these are founded the 

 two systems of classification which are now in vogue. One of 

 these is termed the Linnaean System, after its founder; or the 

 Artificial System, from its character : the other is termed the 

 Natural System. In the Linnaean System, a small number of 

 characters chiefly the number of stamens and pistils is taken 

 as the standard ; and the whole Vegetable Kingdom is distributed 

 underclasses and orders, according to the correspondences and 

 differences among the several genera in these respects, no regard 

 whatever being had to any other characters. In the Natural 

 System, all the characters of the genera are studied ; and those 

 are united into orders, which present the greatest correspondence 

 in the characters that are regarded as of the most importance : 

 on the same principle, the orders are united into classes. If the 

 former plan be followed, genera most widely differing in their 

 structure and physiological characters are often brought together, 

 and others which are nearly allied are frequently separated to a 

 great extent ; so that in fact, it is very common to find, that 

 nothing can be stated as true of all the plants included in a 

 Linnaaan order, except that they have a similar number of sta- 

 mens and pistils. On the other hand, in the Natural System, 

 the number of characters, in which there is a general agreement 

 among all the plants of a particular order, is so great that, to say 

 that the plant belongs to a certain order, is at once to give the 

 greater part of its description. This is the case also in the 

 highest or most general groups. For instance, to say that a par- 

 ticular species is an Exogen, is at once to make known the 

 structure of its stem and the mode of its increase, to express 

 the important fact that it has two cotyledons or seed-leaves, to 

 render it most probable that the arrangement of the veins in its 

 leaves is reticulated rather than parallel, and to intimate that 

 the parts of its flowers are likely to be arranged in fives or fours, 

 rather than in threes. 



