ILLUSTRATIONS OF THE NATUEAL ORDERS. 373 



731. The arrangement and general character of the principal 

 orders under each class form the" subject of the ensuing chapter. 

 Before entering upon it, the 



732. Nomenclature of Orders, Tribes, &C. requires some explanation. 

 The names of such groups are in the plural number. As a gen- 

 eral rule, the name of an order ia that of some leading or well-known 

 genus in it, prolonged into the adjective termination acete. Thus, 

 the plants of the order which comprises the Mallow (Malva) are 

 called MalvacetJB ; that is, Plantm Malvacece, or, in English, Malva- 

 ceous plants : those of which the Rose (Rosa) is the well-known 

 representative are Rosacece, or Eosaceous plants, &c. Some few 

 ordinal names, however, are differently formed, and directly indicate 

 a characteristic feature of the group ; as, for instance, Leguminosts, 

 or the Leguminous plants, such as the Pea, Bean, &c., whose fruit 

 is a legume (610) ; UmbeUiferce, or Umbelliferous plants, so named 

 from having the flowers in umbels ; Gompositce, an order having 

 what were termed compound flowers by the earlier botanists (394) ; 

 Labiatce, so called from the labiate or two-lipped corolla which 

 nearly all the species' exhibit ; Cruciferce, which have their four 

 petals disposed somewhat in the form of a cross (Fig. 405). 



733. Suborders, tribes, and all other groups between orders and 

 genera, bear names framed upon the same principles, that is, they 

 are plural, substantively-taken adjectives, derived from the name of 

 some characteristic .genus of the group. Thus the genus Rosa 

 gives name to a particular tribe. Rosea, of the order Rosacece ; the 

 genus Malva to the tribe Malvern, of the order Malvacece, &c., — the 

 termination in acece being avoided, because reserved for ordinal 



CHAPTEE III. 



ILLUSTRATIONS OF THE NATURAL ORDERS OR FAMILIES. 



734. Some authors (such as Jussieu and Endlicher) commence 



with the lower extremity of the series, and end with the higher ; 



while others (as De Candolle) pursue the opposite course, beginning 



with the more perfect Flowering plants, and concluding with the 



32 



