characters of these, botanists have bestowed the liighest degree 

 of attention, and the student's progTess will depend chiefly upon 

 liis acquaintance with them. 



356. Orders are formed by associating- together those genera 

 which are the most nearly alhed to each other, or to some one 

 genus previonsly assumed as the type. Therefore, as the spe- 

 cies form genera, so genera form orders. 



357. In sj^stematic works, the orders are also associated on 

 natural principles into alliances, groitps, &c., which are inter- 

 mechate between these and the sub-classes, and are designated 

 numerically, thus, group 1st, gi'oup 2d, &;c., or by names derived 

 from a leading order. 



358. Li regard to their extent.the orders differ very widely, 

 some consisting of a single genus, as SaiTaceniacccC, while 

 others comprehend hundreds of genera, as Compositce. For 

 convenience' sake the larger orders are broken up into sub- 

 orders, or tribes. 



359. The Natural System, with its classes and subordinate 

 divisions, may be exhibited in one view ; 



The Vegetable Kingdom is separated 



1st, into Grand Divisions and Subdivisions. 



2nd, " Classes. 



3d, " Sub-classes, Alliances, and Groups. 



4th, " Orders and Sub-orders. 



5th, " Genera and Sub-genera. 



6th, " Species and Varieties, and 



7 th, " Individuals. 



