326 TAXONOMY. 



650. This is the common framework of natural history classi- 

 fication. All plants and all animals belong to some species ; 

 every species to some genus ; every genus to some order or 

 family ; every order to some class ; every class to one or the 

 other kingdom. 1 But this framework, although all that is re- 

 quisite in some parts of natural history, does not express all the 

 observable gradations of relationship among species. And even 

 gradations below species have sometimes to be classified. The 

 series is capable of extension ; and extension is often requisite 

 on account of the large number of objects to be arranged, and 

 the various degrees of relationship which may come into view. 



651. This is effected by the intercalation of intermediate 

 grades, to be introduced into the system only when there is 

 occasion for them. And in botan}^ one or more grades superior 

 to the classes are needful ; for first and foremost is the great 

 division of all plants into a higher and a lower SERIES 2 (or sub- 

 kingdom) , the Phaenogamous and the Cryptogamous. 



652. The grades intercalated into the long-established sequence 

 of Class, Order, Genus, and Species, with new names, are mainly 

 two, Tribe and Cohort. 



653. Tribe has been for a generation or two thoroughly estab- 

 lished in both kingdoms, as a grade inferior to order and supe- 

 rior to genus. In botanical classification, much use is made of 

 this grade, genera being grouped into tribes. 



654. Cohort (Lat. Cohors) is of more recent introduction, at 

 least in Botany, but is becoming established for a grade next 

 above that of order. Orders are grouped into cohorts. Lindley 

 hit upon a good English name for this grade, that of Alliance. 

 But this word has no available Latin equivalent ; while cohort 

 takes equally well a Latin or an English form. 



655. Finally, each grade is capable of being doubled by the 

 recognition of one like it and immediately subordinate to it, and 

 with designation directly expressive of the subordination. For 



1 Not recognizing Haeckel's third kingdom of Protista, consisting of those 

 lowest forms of being from which the animal and vegetable kingdoms 

 emerge. 



2 Answering to the French Embranchement in zoology. For this it is pro- 

 posed to use the word Division (Divisio) : see Laws of Botanical Nomencla- 

 ture adopted by the International Botanical Congress held at Paris in 

 August, 1867 ; together witli a Historical Introduction and a Commentary, by 

 Alph. DeCandolle, English translation, London, 1868 ; the original French 

 edition, Paris, 1867. Perhaps no better name can be found ; but the elder 

 DeCandolle brought Dirisio into common use for a grade subordinate to 

 tribe. Endlicher employed the term Regio. We have used Series, and 

 much prefer it. 



