CLASSIFICATION OF PLANTS. 47 



cnliar cliaractoristics, and the species spenrmint nil the individual mints of 

 this kind. 



But tliese two species bear an evident relationship to each other, as 

 evinced by their square stems, opposite leaves, peculiar flowers and seeds, 

 as well as in their similar but distinct aromati(! in-operties. This relation- 

 ship is expressed by the term genus, which signifies n group of relatejd 

 species. 



J^it if we investigate a little further we shall find nuuiy other plants 

 having a general reseniblance to these two mints in their manner of 

 growth, mode of flowering, etc. Take catnip, for example. Her(> we find 

 the squai'e stem, opposite leaves, and a similar mode of flowering, but still 

 some well-marked ditt'erences which have placed it in another genus. But 

 these two genera have still marks of relationship wliicsh pl;u;e them, to- 

 gether with many other genera, in a still greater group termed an order. 

 Nor do we stop here, for we have seen that a plant may have i)olypetalous, 

 gamopetalous, or apetalous flowers, and obviously orders of polypetalic are 

 more nearly related to each other than to gamopetahe or ai)etahe ; hence 

 oi'ders are grouped in divisions. And again, the three divisions of poly- 

 petakc, gamopetahe, and apetahe, being found in exogenous plants, are 

 more nearly related to each other than to endogenous plants ; hence 

 tlie distinction of classes. But the two classes of flowering plants are 

 yet more neai'ly related to each other than to flowerless plants, and an- 

 other term, Sub-kingdom, is required to express that fact. 



To express tliis grouping of i)lants in a natural way we have : Sub" 

 kingdom. Class. Division. Order. Genus. Species. 



In this system of classification the order, genus, and species has each its 

 distinctive name. Names of orders are often derived from some well- 

 marked characteristic of the plants composing it, as JaJiiaUr, an order 

 characterized by labiate flowers ; Icr/uminoxd', having fruit in the form of a 

 legume ; crucifern', having flowers in the form of a cross. Often, again, 

 they are derived from that of some genus which they include whose name 

 was established before this classification was introduced, as magnoliacece, 

 from magnolia ; rainmculacece, from ranunculus ; rosacea;, from rose ; sola- 

 naci'cn, from solanum, etc. 



The generic name is in many instances of ancient origin ; in other in- 

 stances it has been derived from names of individuals or from some 

 structural peculiarity, etc. 



The specific name most commonly characterizes some structui'al feature : 

 Gentiana quinquc flora {Jive-fioiocred G.), G. criidta {fringed G.), etc. It not 

 unfrequently commemorates some individual or coixntry, as Gentiana An- 

 drewHii {Andrews gentian), Comas Canadensis, etc., and is then commonly 

 written with an initial capital. 



To illustrate the manner in which these names are employed, we will 

 make use of a single example. The order GEXTUNACEiE includes all plants 



