LINNJEAN SYSTEM. 243 



The orders of the 19th class are known by the inter- 

 blending of florets, which are united or separate, fer- 

 tile or barren. 



1. Polygainia Equalis has them all united, and all 

 fertile. 



2. Polygamia Superflua, has united discal florets, while 

 those of the ray produce pistils only, and all fertile. 



3. Polygamia Frustranea has united discal florets, 

 while those of the ray, whether they produce pistils 

 or not, are unfertile. 



4. Polygamia Necessaria has discal florets with stamens 

 only, while those of the ray have only pistils. 



i. Polygamia Segregata has several florets, each with a 



proper calyx and united anthers, all included in one 



common calyx. 



The orders of the 20th, 21st and 22d classes are dis- 

 tinguished by the number of their stamens. 



The 23d class has three orders. Monoecia has the 

 different kinds of flowers all confined to one plant. 

 Dioecia has its several kinds of flowers on two plants, 

 and Trioecia has them on three separate plants. 



The orders of the 24th class are Ferns, Mosses, 

 Hepaticce, Algce including the Lichens, and Fungi. 



Monandria. — The class Monandria contains two orders 

 exemplified in Salicornia and Blitum, both American 

 plants. It is by no means extensive, and if we ex- 

 cept the Scitamineos natives of tropical regions it 

 is by by no means aD interesting or important class. 



Diandria has three orders, but one of which occurs in 

 the United States, unless we choose to separate 

 Anthoxanthum from the genus to which it belongs. 

 It comprehends the Jasmineaz of Jussieu, and a 

 few of tne Labiate flowers such asRosemary and Sage. 



