THE PRINCIPLES OF CLASSIFICATION. 327 



example, if Dicotyledones and Monocotyledones be the two 

 classes of Phaenogamia, the former (and only the former) is 

 divided upon very important characters into two branches, of far 

 higher rank than the cohorts, viz. the Angiospermae and the 

 Gymnospermse, which take the name of SUBCLASSES. Orders, 

 especially the more comprehensive ones, often comprise two or 

 more groups so distinct that it may fairly be a question whether 

 they are not of ordinal rank : such take the name of SUBORDERS. 

 Tribes in like manner may comprise groups of similar relative 

 value : these are SUBTRIBES. Genera may comprise sections of 

 species which might almost as well rank as genera themselves : 

 to mark their importance and pretension (which may come to 

 be allowed) , they are termed SUBGENERA. Finally, forms which 

 are ranked as varieties, but which may establish a claim to be 

 distinct species, are sometimes termed SUBSPECIES. Even what 

 we regard as a variety may comprise more or less divergent 

 forms, to be distinguished as SUB VARIETIES. 



656. Some of the larger and most diversified orders, tribes, 

 genera, or species may require all these analytical appliances, 

 and even more, for their complete elucidation ; while others, 

 comparatively homogeneous, offer no ground for them. But 

 when these grades, or some of them, come into use, they are 

 always in the following sequence : 



KINGDOM, 



SERIES or Division, or Sub-kingdom, 

 CLASS, 



Subclass, 

 Cohort, 



ORDER or Family, 

 Suborder, 

 TRIBE, 

 Subtribe, 

 GENUS, 



Subgenus, 

 Section, 



Subsection, 

 SPECIES, 



Subspecies or Race, 

 Variety, 



Subvariety. 



657. Nature and Meaning of Affinity. These grades, the higher 

 including the lower, denote degrees of likeness or difference. 

 Plants belonging respectively to the two great series or primary 

 divisions may accord only in the most general respects, in that 

 which makes them plants rather than animals. Plants of the 

 same variety are generally as much alike as if they were of the 



