Xviii INTRODUCTION. 



The Orders of the Sixteenth, Seventeenth, and 

 Eighteenth Classes, MONADELPHIA, DIADELPHIA, and 

 POLYADELPHIA, depend on the number of the stamens : 

 thus, Class MONADELPHIA, Order PENTANDRIA, includes 

 plants having five stamens united by their filaments into 

 one set ; Class DIADELPHIA, Order DECANDRIA, plants 

 having ten stamens combined by their filaments into 

 two sets ; and Class POLYADELPHIA, Order POLYANDRIA, 

 plants with more than twenty stamens combined by their 

 filaments into three or more sets. 



In the Nineteenth Class, SYNGENESIA, the Orders de- 

 pend on the structure and arrangement of the florets ; 

 but as they are Orders nearly identical with the Groups 

 into which the COMPOUND FLOWERS are distributed, their 

 limits need not be assigned here. 



In the Twentieth, Twenty-first, and Twenty-second 

 Classes, GYNANDRIA, MONCECIA, and DICECIA, the Orders 

 are determined by the number of the stamens. Plants, 

 for example, having one stamen are in the Order MON- 

 ANDRIA ; those with two stamens, in the Order DIAN- 



DRIA, &C. 



The Twenty-third Class, POLYGAMIA, contains only 

 one British Order, namely, MONCECIA, in which there are 

 three different kinds of flowers those with stamens 

 only, those with pistils only, and those with both sta- 

 mens and pistils on the same plant. 



As the limits of this volume exclude all mention of 

 the plants in the extensive Class CRYPTOGAMIA, it is 

 not necessary to enumerate the Orders into which it is 

 divided. 1 



(1). The student is recommended to commit to memory the names, rather 

 than the numbers of the Classes and Orders. While he does this he will find 

 it useful to bear in mind that the names both of Classes and Orders are of 

 Greek etymology, and that the prefixes are mostly numerals. Thus, mow 

 signifies one ; di, two ; tri, three ; tetra, four ; pent, five ; hex, six ; hepta, 

 seven ; oct, eight ; enne, nine ; dec, ten ; dodec, twelve ; icos, twenty ; and 

 poly, many. The root dynam signifies power or excess : thus, Didynamia 

 means "the excess of two ;" Tetradynamia, "the excess of four." Adelphia 

 signifies a brotherhood, as Monadelphia, "one brotherhood," or united set of 

 stamens ; Syngenesia signifies " a growing together," in allusion to the com- 

 bination of the anthers in that class. The termination ceci denotes " a house- 



