THE CLASSIFICATION OF PLANTS. 401 



country, and which have been accordingly adopted in this work, 

 are, Acotyledones, Monocotyledones, and Dicotyledones, — terms 

 which, as Ave have already explained, are derived from the struc- 

 tui'e of the embryo in the three classes respectively. Other 

 tei-ms also in common use, are derived from the absence or pre- 

 sence of a stem, and its mode of development : such are Exogens, 

 Endogens, Acrogens, and Thallogens. The above names are 

 used ct^pecially in what are called Natural Systems of Classifi- 

 cation ; while the names of Classes in the Artificial System of 

 Linnffius, are derived chiefly from the number and other cha- 

 racters presented by the stamens (page 406). 



The names of the Orders in the Artificial System of Linnaeus 

 are chiefly derived from the pistil and fi-uit. Those of Natural 

 Systems are usually taken from some well-known genus which 

 is included in any particular order, and Avhich may be regarded 

 as the type of that order. Thus the genus Ranunculus gives the 

 name Ranunculacece to the order to which it belongs; the genera 

 Papaver, Malva, Hypericum, Geranium, Rosa, Lilium, Orchis, 

 Iris, &c., in like manner, give names respectively, to the orders 

 Papaveracece, Malvacece, Hypericacece, Gera?uacece, Bosacece, Li- 

 liacece, OrchidacecB, Iridacece, &c. At other times, the names of 

 the orders are derived from some characteristic feature which the 

 plants included in them present. Thus the order Cruciferce 

 is so named, because the species it includes, have the four petals 

 of their flowers arranged in a cross-like form; the order Legu- 

 minosce comprises plants whose fruit is a legume; the Umbel- 

 lifercB are umbel-bearing plants; the Labiatce have a labiate 

 corolla; the ConifercE are cone-bearing plants ; and so on. 



The names of genera are derived in various ways: thus either 

 from the natne of some eminent botanist, as Linnjea after Lin- 

 nffius, Smithia after Smith, Hookeria after Hooker, Jussisea after 

 Jussieu, Toumefortia after Tournefort, &c. ; or from some pecu- 

 liarity of structure, or habit, and various other circumstances. 

 Thus, Crassula is derived from the genus comprising plants with 

 succulent or thickened leaves; Dentaria derives its name from 

 presenting dentate roots ; Arenaria from growing in sandy 

 pla(;es ; Lithospermum from its seeds or properly achaenia having 

 a stony hardness ; and so on. 



The names of species are also variously derived. The specific 

 names are usually written after the generic, and these taken toge- 

 ther constitute the proper appellation of a plant. The species of 

 the genus Viola, as shown by Gray, exhibit the origin of many 

 specific names. " Thus, specific names sometimes distinguish the 

 country which a plant inhabits, for example, Viola canadensis, the 

 Canadian Violet; or the station where it naturally grows, as Viola 

 palustris, which grows in swamps, Viola arvensis, in fields, &c, ; 

 or they express some obvious character of the species, as Viola 

 rostrata, where the corolla bears a remarkably long spur, Viola 



