The Classification of Plants 439 



and when used to name plants of a given locality, but they are 

 very unsatisfactory when used to name plants in widely separated 

 locahties. For example, the white and black oaks of California 

 are not the same trees as the white and black oaks of Pennsyl- 

 vania. The white pine of New England is not the same as the 

 white pine of Colorado, and both differ from the white pine of 

 Idaho. Consequently taxonomists, or students of classification, 

 have been forced to give each kind of plant a scientific name. 

 This name consists of two words having a Latin or Greek form : 

 (i) a genus name and (2) a species name. The name for the oak 

 genus is the old Latin word for oak, Quercus; for the species 

 called '' white oak " in the eastern United States, Quercus alba 

 (Latin for '' white ") ; for the California white oak, Quercus lohata. 



Larger groups. Similar individuals, then, are grouped into 

 species, and species having certain fundamental characters in 

 common are placed together in a genus. In a similar way genera 

 are grouped into families, and families are grouped into orders. 

 Several orders taken together form a class, and a group of classes 

 forms a phylum (or division) of the plant kingdom. In some of 

 the largest phyla it may be convenient to recognize secondary 

 divisions in each of these groups, such as subclass, suborder, 

 subfamilies, and subgenera. Highly variable species are some- 

 times subdivided into varieties. 



The following diagram showing the higher groups to which 

 ^ the oaks belong will help to make these groupings clear : 



THE PLANT KINGDOM 

 Phylum — Angiospermae 



I. Class — Dicotyledoneae (Includes more than 25 orders of plants 

 whose embryos have 2 cotyledons) 

 a. Order — ■ Fagales (Includes Birch and Beech families) 



(i) Family — Fagaceae (Beeckfamily) (Includes genera of Beech 

 Oak, Chestnut, etc.) 



(a) Genus — Quercus (Oak) (Includes more than 200 species 

 mostly in North America and Asia) 



