178 CLASSIFICATION. [SECTION 18. 



529. Orders are groups of genera that resemble each other; that is, 

 they are to genera what genera are to species. As familiar illustrations, 

 the Oak, Chestaut, and Beech genera, along with the Hazel genus and the 

 Hornbeams, all belong to one order. The Birches and the Alders make 

 another; the Poplars and Willows, another; the Walnuts (with the But- 

 ternut) and the Hickories, still another. The Apple genus, the Quince 

 and the Hawthorns, along with the Plums and Cherries and the Peach, 

 the Raspberry with the Blackberry, the Strawberry, the Rose, belong 

 to a large order, which takes its name from the Rose. Most botanists 

 use the names "Order" and " Family " synonymously; the latter more 

 popularly, as "the Rose Family," the former more technically, as 

 "Order Rosacea." 



530. But when the two are distinguished, as is common in zoology, 

 Family is of lower grade than Order. 



531. Classes are still more comprehensive assemblages, or great groups. 

 Thus, in modern botany, the Dicotyledonous plants compose one class, 

 the Monocotyledonous plants another (36-40). 



532. These four grades, Class, Order, Genus, Species, are of universal 

 use. Variety comes in upon occasion. For, although a species may have 

 no recognized varieties, a genus implies at least one species belonging to 

 it ; every genus is of some order, and every order of some class. 



533. But these grades by no means exhaust the resources of clas- 

 sification, nor suffice for the elucidation of all the distinctions which 

 botanists recognize. In the first place, a higher grade than that of class 

 is needful for the most comprehensive of divisions, that of all plants into 

 the two Series of Phanerogamous and Cryptogamous (6) ; and in natu- 

 ral history there are the two Kingdoms or Realms, the Vegetable and 

 the Animal. 



534. Moreover, the stages of the scaffolding have been variously ex- 

 tended, as required, by the recognition of assemblages lower than class but 

 higher than order, viz. Subclass and Cohort; or lower than order, & Sub- 

 order; or between this and genus, a Tribe ; or between this and tribe, a 

 Subtribe ; or between genus and species, a Subgenus; and by some a 

 species has been divided into Subspecies, and a variety into Subvarieties. 

 Last of all are Indioiduals. Suffice it to remember that the following are 

 the principal grades in classification, with the proper sequence ; also that 

 only those here printed in small capitals are fundamental and universal 

 in botany: — 



Series, 



Class, Subclass, Cohort, 



Order, or Family, Suborder, Tribe, Subtrttw, 

 Genus, Subgenus or Section, 

 Species, Variety, 



