CLASSIFICATION OF PLANTS. 47 



culiar characteristics, and the sjDecies spearmint all the iudividual mints of 

 this kind. 



But these 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 aromatic proj^erties. This relation- 

 ship is expressed by the term genus, which signifies a gi'oup of related 

 species. 



But if we investigate a little further we shall find many other plants 

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

 growth, mode of flowering, etc. Take catnip, for example. Here we find 

 the square stem, opposite leaves, and a similar mode of flowering, but still 

 some well-marked differences which have placed it in another genus. But 

 these two genera have still marks of relationship which place 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 polypetalous, 

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

 more nearly related to each other than to gamoi^etaliB or apetalse ; hence 

 orders are grouped in divisions. And again, the three divisions of poly- 

 petalte, gamopetalae, and aj^etahe, being found in exogenous plants, are 

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

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

 yet more nearly related to each other than to flowerless plants, and an- 

 other term, sub-kingdom, is requii-ed to express that fact. 



To express this grouping of plants 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 lahiake, an order 

 characterized by labiate flowers ; leguminosce, ha\dng fruit in the form of a 

 legaime ; crucifenv, 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 ; ?-a»M?ici<Zacece, from ranunculus ; rosacea, from rose ; sola- 

 nacece, 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 structural feature : 

 Gentiana quinqucfiora {five-flowered G.), G. crinita {fringed G.), etc. It not 

 unfi-equently commemorates some individual or country, as Gentiana An- 

 drewsii {Andrews' gentian), Cornus 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 Gentianacex includes all plants 



